Bipolar electrosurgical clamp for removing and modifying tissue

ABSTRACT

The present invention provides systems, apparatus and methods for selectively applying electrical energy to body tissue in order to ablate, contract, coagulate, or otherwise modify a target tissue or organ. The closed configuration is adapted for clamping and coagulating a target tissue while the apparatus is operating in the sub-ablation mode, while the open configuration is adapted for ablating the target tissue via molecular dissociation of tissue components. A method of the present invention comprises clamping a target tissue or organ with an electrosurgical probe. A first high frequency voltage is applied between the active electrode and the return electrode to effect coagulation of the clamped tissue. Thereafter, a second high frequency voltage is applied to effect localized molecular dissociation of the coagulated tissue.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 09/839,427 filed Apr. 20, 2001 now U.S. Pat. No. 6,974,453,which is a continuation-in-part of U.S. patent application Ser.No.09/780,745 filed Feb. 9, 2001, now U.S. Patent No. 6,770,071 thecomplete disclosures of which are incorporated herein by reference forall purposes.

The present invention is also related to commonly assigned U.S.Provisional Patent Application No. 60/062,996, filed Oct. 23, 1997, U.S.patent application Ser. No. 08/990,374, filed Dec. 15, 1997, which is acontinuation-in-part of U.S. patent application Ser. No. 08/485,219,filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, patent applicationSer. Nos. 09/109,219, 09/058,571, 08/874,173 and 09/002,315, filed onJun. 30, 1998, Apr. 10, 1998, Jun. 13, 1997, and Jan. 2, 1998,respectively) and U.S. patent application Ser. No. 09/054,323, filed onApr. 2, 1998, U.S. patent application Ser. No. 09/010,382, filed Jan.21, 1998, and U.S. patent application Ser. No. 09/032,375, filed Feb.27, 1998, U.S. patent application Ser. No. 08/977,845, filed on Nov. 25,1997, Ser. No. 08/942,580, filed on Oct. 2, 1997, U.S. application Ser.No. 08/753,227, filed on Nov. 22, 1996, U.S. application Ser. No.08/687,792, filed on Jul. 18, 1996, and PCT International Application,U.S. National Phase Serial No. PCT/US94/05168, filed on May 10, 1994,now U.S. Pat. No. 5,697,909, which was a continuation-in-part of U.S.patent application Ser. No. 08/059,681, filed on May 10, 1993, which wasa continuation-in-part of U.S. patent application Ser. No. 07/958,977,filed on Oct. 9, 1992 which was a continuation-in-part of U.S. patentapplication Ser. No. 07/817,575, filed on Jan. 7, 1992, the completedisclosures of which are incorporated herein by reference for allpurposes. The present invention is also related to commonly assignedU.S. Pat. No. 5,683,366, filed Nov. 22, 1995, the complete disclosure ofwhich is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

The present invention generally relates to electrosurgical systems andmethods for ablating, severing, contracting, or otherwise modifyingtarget tissues or organs. The invention relates more particularly toelectrosurgical apparatus and methods for coagulating a tissue or organand for ablating the coagulated tissue or organ via moleculardissociation of tissue components. The present invention further relatesto electrosurgical methods and apparatus for clamping a target tissue orblood vessel prior to coagulating and severing the tissue or bloodvessel.

Conventional electrosurgical instruments and techniques are widely usedin surgical procedures because they generally reduce patient bleedingand trauma associated with cutting operations, as compared withmechanical cutting and the like. Conventional electrosurgical proceduresmay be classified as operating in monopolar or bipolar mode. Monopolartechniques rely on external grounding of the patient, where the surgicaldevice defines only a single electrode pole. Bipolar devices have twoelectrodes for the application of current between their surfaces.Conventional electrosurgical devices and procedures, however, sufferfrom a number of disadvantages. For example, conventionalelectrosurgical cutting devices typically operate by creating a voltagedifference between the active electrode and the target tissue, causingan electrical arc to form across the physical gap between the electrodeand the tissue. At the point of contact of the electric arcs with thetissue, rapid tissue heating occurs due to high current density betweenthe electrode and the tissue. This high current density causes cellularfluids to rapidly vaporize into steam, thereby producing a “cuttingeffect” along the pathway of localized tissue heating. Thus, the tissueis parted along the pathway of evaporated cellular fluid, inducingundesirable collateral tissue damage in regions surrounding the targettissue.

Further, monopolar electrosurgical devices generally direct electriccurrent along a defined path from the exposed or active electrodethrough the patient's body to the return electrode, the latterexternally attached to a suitable location on the patient. This createsthe potential danger that the electric current will flow throughundefined paths in the patient's body, thereby increasing the risk ofunwanted electrical stimulation to portions of the patient's body. Inaddition, since the defined path through the patient's body has arelatively high electrical impedance, large voltage differences musttypically be applied between the return and active electrodes in orderto generate a current suitable for ablation or cutting of the targettissue. This current, however, may inadvertently flow along body pathshaving less impedance than the defined electrical path, which willsubstantially increase the current flowing through these paths, possiblycausing damage to or destroying surrounding tissue.

Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient. In bipolar electrosurgical devices, both the active andreturn electrode are typically exposed so that both electrodes maycontact tissue, thereby providing a return current path from the activeto the return electrode through the tissue. One drawback with thisconfiguration, however, is that the return electrode may cause tissuedesiccation or destruction at its contact point with the patient'stissue. In addition, the active and return electrodes are typicallypositioned close together to ensure that the return current flowsdirectly from the active to the return electrode. The close proximity ofthese electrodes generates the danger that the current will short acrossthe electrodes, possibly impairing the electrical control system and/ordamaging or destroying surrounding tissue.

In addition, conventional electrosurgical methods are generallyineffective for ablating certain types of tissue, and in certain typesof environments within the body. For example, loose or elasticconnective tissue, such as the synovial tissue in joints, is extremelydifficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to, or in contact with, the elastic tissue for a sufficientperiod of time to energize the electrode and conduct current through thetissue.

There is a need for a general-purpose electrosurgical apparatus adaptedfor the precise removal or modification of a target tissue or organ at aspecific location, wherein the target tissue or organ can be ablated,severed, resected, contracted, and/or coagulated, with minimal, or no,collateral tissue damage. The instant invention provides such anapparatus and related methods, wherein the apparatus includes at leastone moveable electrode, and at least a portion of the target tissue ororgan may be clamped between an active electrode and a return electrodeprior to coagulation of the tissue or organ. Following coagulation, thecoagulated tissue or organ may be ablated or severed.

SUMMARY OF THE INVENTION

The present invention generally provides systems, apparatus, and methodsfor selectively applying electrical energy to cut, incise, ablate, orotherwise modify a tissue or organ of a patient. In one aspect, theelectrosurgical systems and methods of the invention are useful forresecting a tissue or organ having a plurality of blood vessels runningtherethrough, wherein, using a single probe, each blood vesselencountered during resection of the tissue or organ may be clamped,coagulated, and then severed.

In one aspect, the present invention provides a method of creating anincision in a body structure. An electrosurgical probe is positionedadjacent the target tissue so that one or more active electrode(s) arebrought into at least partial contact or close proximity with the targettissue. High frequency voltage is then applied between the activeelectrode(s) and one or more return electrode(s) and the activeelectrode(s) are moved, translated, reciprocated, or otherwisemanipulated to cut through a portion of the tissue. In some embodiments,an electrically conductive fluid, e.g., isotonic saline or conductivegel, is delivered or applied to the target site to substantiallysurround the active electrode(s) with the fluid. In other embodiments,the active electrode(s) are immersed within the electrically conductivefluid. In both embodiments, the high frequency voltage may be selectedto locally ablate or sever a target tissue, and/or to effect acontrolled depth of hemostasis of severed blood vessels within thetissue.

In one aspect, tissue is cut or otherwise modified by moleculardissociation or disintegration processes. (In contrast, in conventionalelectrosurgery tissue is cut by rapidly heating the tissue untilcellular fluids explode, producing a cutting effect along the pathway oflocalized heating.) The present invention volumetrically removes thetissue along the cutting pathway in a cool ablation process thatminimizes thermal damage to surrounding tissue. In these embodiments,the high frequency voltage applied to the active electrode(s) issufficient to vaporize the electrically conductive fluid (e.g., gel orsaline) between the active electrode(s) and the tissue. Within thevaporized fluid, a plasma is formed and charged particles (e.g.,electrons) cause the molecular breakdown or disintegration of thetissue, perhaps to a depth of several cell layers. This moleculardissociation is accompanied by the volumetric removal of the tissue,e.g., along the incision of the tissue. This process can be preciselycontrolled to effect the volumetric removal of tissue as thin as 10microns to 150 microns with minimal heating of, or damage to,surrounding or underlying tissue structures. A more complete descriptionof this phenomenon is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

Apparatus according to the present invention generally include anelectrosurgical instrument, such as a probe or catheter, having a shaftwith proximal and distal ends, one or more active electrode(s) at thedistal end and one or more connectors coupling the active electrode(s)to a source of high frequency electrical energy. The active electrode(s)are preferably designed for cutting tissue; i.e., they typically have adistal edge or point. In one embodiment, a plurality of activeelectrodes are aligned with each other to form a linear electrode arrayfor cutting a path through the tissue. In another exemplary embodiment,the active electrode(s) include a sharp distal point to facilitate thecutting of the target tissue. In one specific configuration, the activeelectrode is a blade having a sharp distal point and sides. As the sharpdistal point incises the tissue, the sides of the blade slidinglycontact the incised tissue. The electrical current flows through thatportion of the tissue in the vicinity of the active electrode and/or theconductive fluid to the return electrode, such that the target tissue isfirst severed, and then the severed tissue is coagulated.

The apparatus can further include a fluid delivery element fordelivering electrically conductive fluid to the active electrode(s) andthe target site. The fluid delivery element may be located on the probe,e.g., a fluid lumen or tube, or it may be part of a separate instrument.Alternatively, an electrically conductive gel or spray, such as a salineelectrolyte or other conductive gel, may be applied the target site. Inthis embodiment, the apparatus may not have a fluid delivery element. Inboth embodiments, the electrically conductive fluid preferably providesa current flow path between the active electrode(s) and one or morereturn electrode(s). In an exemplary embodiment, the return electrode islocated on the probe and spaced a sufficient distance from the activeelectrode(s) to substantially avoid or minimize current shortingtherebetween and to shield the return electrode from tissue at thetarget site.

In a specific configuration, the electrosurgical probe includes anelectrically insulating electrode support member having a tissuetreatment surface at the distal end of the probe. One or more activeelectrode(s) are coupled to, or integral with, the electrode supportmember such that the active electrode(s) are spaced from the returnelectrode. In one embodiment, the probe includes a plurality of activeelectrode(s) having distal edges linearly aligned with each other toform a sharp cutting path for cutting tissue. The active electrodes arepreferably electrically isolated from each other, and they extend about0.2 mm to about 10 mm distally from the tissue treatment surface of theelectrode support member. In this embodiment, the probe may furtherinclude one or more lumens for delivering electrically conductive fluidto one or more openings around the tissue treatment surface of theelectrode support member. In an exemplary embodiment, the lumen extendsthrough a fluid tube exterior to the probe shaft that ends proximal tothe return electrode.

In another aspect of the invention, there is provided an electrosurgicalprobe having a blade-like active electrode affixed to an electricallyinsulating electrode support on the distal end of a shaft. In a specificconfiguration, the active electrode is in the form of a blade,comprising a substantially flat metal blade having at least one activeedge and first and second blade sides. In one embodiment, the activeelectrode comprises a hook. The hook may include a curved portion. Oneor more portions of the hook may have a serrated edge. The returnelectrode is typically located on the shaft distal end proximal to theelectrode support. In use, the active electrode and the return electrodeare coupled to opposite poles of a high frequency power supply. Theactive edge may have a variety of shapes, and is adapted for generatinghigh current densities thereon, and for precisely severing or ablatingtissue or an organ in a highly controlled manner via moleculardissociation of tissue components. The first and second blade sides areadapted for engaging with tissue, such as tissue severed by the activeedge, and for coagulating tissue engaged therewith.

According to one aspect of the invention, there is provided a method formodifying a tissue using an electrosurgical probe having an activeelectrode in the form of a single blade which includes at least oneactive edge and first and second blade sides. The method involvespositioning the probe such that the active electrode makes contact with,or is in close proximity to, a target tissue; and applying a highfrequency voltage between the active and return electrodes sufficient toprecisely sever or remove target tissue via molecular dissociation oftissue components adjacent to the active edge. The probe may bemanipulated during the application of the high frequency voltage suchthat the active electrode is moved with respect to the target tissue.According to one aspect of the invention, the configuration of theactive electrode (e.g., a hook shaped electrode) is adapted for severingtissue as the probe distal end is drawn or pulled towards the operatorof the probe. In this manner, the extent to which the tissue is severedcan be precisely controlled. Thereafter, the severed tissue may becoagulated upon engagement of the tissue against the first and secondblade sides of the active electrode.

According to one aspect of the invention, there is provided anelectrosurgical system including a probe having a shaft distal end. Anactive electrode and a return electrode are disposed at the shaft distalend. At least one of the active electrode and the return electrode aremoveable, such that the probe can adopt an open configuration or aclosed configuration. In the open configuration, a target tissue ororgan may be positioned between the active and return electrodes, andthereafter the probe may be urged towards the closed configuration suchthat the target tissue or organ is effectively clamped between theactive and return electrodes. While the target tissue or organ is thusclamped, a suitable high frequency voltage may be applied between theactive and return electrodes so as to coagulate the tissue or organ.Thereafter, the coagulated tissue or organ may be unclamped or releasedby forcing the probe towards the open configuration. With the targettissue or organ in at least close proximity to the active electrode, asecond high frequency voltage may be applied between the active andreturn electrodes so as to ablate or sever the coagulated tissue ororgan via localized molecular dissociation of tissue components.

In one embodiment, the probe is shifted between the open and closedconfigurations via an actuator unit including at least one of a clampunit and a release unit. In one aspect, actuation of the actuator unitserves to switch the electrosurgical system, via a mode switch, betweenan ablation mode and a sub-ablation mode. In another aspect, a modeswitch is responsive either to a change in configuration of the probebetween the open and closed configurations, or to movement of a moveableelectrode.

In another aspect, there is provided a bipolar electrosurgical clampincluding a return electrode in the form of a moveable cowl or hood. Inone embodiment, the cowl includes a distal notch for accommodating aportion of the active electrode which protrudes laterally from theprobe. In another embodiment, the moveable cowl includes an undulatingperimeter adapted for gripping a target tissue or organ. In oneembodiment, the moveable cowl is pivotable about its proximal endbetween a closed- and an open configuration. In yet another aspect,there is provided a bipolar electrosurgical clamp including a moveableactive electrode, which can be pivoted between a closed- and an openconfiguration.

The electrosurgical probe of the invention is applicable to a broadrange of procedures, including without limitation: cutting, resection,ablation, and/or hemostasis of tissues and organs such as prostate,liver, bowel, intestine, gall bladder, uterus, tissue in laparascopic oropen surgical procedures (e.g., cholecystectomy, Nissen fundoplication,bowel resection, hysterectomy, adhesiolysis and the like), scar tissue,myocardial tissue, and tissues of the knee, shoulder, hip, and otherjoints; procedures of the head and neck, such as of the ear, mouth,throat, pharynx, larynx, esophagus, nasal cavity, and sinuses; as wellas procedures involving skin tissue removal and/or collagen shrinkage inthe epidermis or dermis. A more detailed account of various treatmentsand procedures which may be carried out according to the invention isset forth in enabling detail hereinbelow.

For a further understanding of the nature and advantages of theinvention, reference should be made to the following description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrosurgical system incorporatinga power supply and an electrosurgical probe for tissue ablation,resection, incision, contraction, vessel harvesting, and hemostasis,according to the present invention;

FIG. 2 is a side view of an electrosurgical probe according to thepresent invention;

FIG. 3 is an end view of the distal portion of the probe of FIG. 2;

FIG. 4 is a cross sectional view of the distal portion of theelectrosurgical probe of FIG. 2;

FIG. 5 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIG. 6 is an end view of an exemplary electrode support comprising amulti-layer wafer with plated conductors for electrodes;

FIGS. 7 and 8 are side views of the electrode support of FIG. 6;

FIGS. 9A-12A are side views of the individual wafer layers of theelectrode support;

FIGS. 9B-12B are cross-sectional views of the individual wafer layers;

FIG. 13 is a side view of an individual wafer layer;

FIGS. 14 and 15 illustrate an alternative multi-layer wafer designaccording to the present invention;

FIG. 16 is a perspective view of an electrosurgical probe having anelongated, blade-like active electrode;

FIG. 17A-17C are cross-sectional views of the distal portions of threedifferent embodiments of an electrosurgical probe according to thepresent invention;

FIG. 18 illustrates an electrosurgical probe with a 90° distal bend anda lateral fluid lumen;

FIG. 19 illustrates an electrosurgical system with a separate fluiddelivery instrument according to the present invention;

FIGS. 20A and 20B are cross-sectional and end views, respectively, ofyet another electrosurgical probe incorporating flattened activeelectrodes;

FIG. 21 is a detailed end view of an electrosurgical probe having anelongate, linear array of active electrodes suitable for use in surgicalcutting;

FIG. 22 is a detailed view of a single active electrode having aflattened end at its distal tip;

FIG. 23 is a detailed view of a single active electrode having a pointedend at its distal tip;

FIG. 24 is a perspective view of the distal portion of anotherelectrosurgical probe according to the present invention;

FIG. 25 illustrates another embodiment of the probe of the presentinvention, specifically designed for creating incisions in external skinsurfaces;

FIG. 26 is a perspective view of another embodiment of anelectrosurgical probe for use in dermatology procedures;

FIGS. 27A-27C are exploded, isometric views of the probe of FIG. 26;

FIG. 28 is a cross-sectional view of another alternative electrosurgicalprobe;

FIG. 29 illustrates another embodiment of the electrosurgical probe ofthe present invention, incorporating additional active electrodes;

FIG. 30 is a perspective view of an electrosurgical probe having a bladeelectrode;

FIG. 31A is a perspective view, and FIG. 31B is a lateral view, of ablade electrode, according to one embodiment of the invention;

FIGS. 32A, 32B, and 32C are a side view, a plan view, and an end view,respectively, of an electrosurgical probe having a blade electrode;

FIGS. 33A and 33B are a side view and a plan view, respectively, of thedistal end of an electrosurgical probe having a terminal bladeelectrode, according to one embodiment of the invention;

FIGS. 33C-33E each show a side view of the distal end of anelectrosurgical probe having a terminal blade electrode, according tothree different embodiments of the invention;

FIGS. 34A, 34B, and 34C are a side view, a plan view, and an end view,respectively, of an electrosurgical probe having a terminal electrodesupport and a lateral blade electrode, according to another embodimentof the invention;

FIGS. 35A, 35B, and 35C are a side view, a plan view, and an end view,respectively, of an electrosurgical probe having a lateral electrodesupport and a lateral blade electrode, according to another embodimentof the invention;

FIGS. 36A and 36B each show a side view of the distal end of anelectrosurgical probe having a blade electrode, according to twodifferent embodiments of the invention;

FIGS. 37A, and 37B are a side view and an end view, respectively, of anelectrosurgical probe having a lumen external to the probe shaft,according to one embodiment of the invention;

FIGS. 38A, and 38B are a side view and an end view, respectively, of anelectrosurgical probe having an outer sheath surrounding the probeshaft, according to another embodiment of the invention;

FIGS. 39A, 39B, and 39C schematically represent a perspective view, alongitudinal sectional view, and an end view, respectively, of anelectrosurgical probe, according to another embodiment of the invention;

FIG. 39D shows detail of the distal portion of the probe of FIGS. 39A-C;

FIGS. 40A and 40B schematically represent a longitudinal sectional view,and an end view, respectively, of an electrosurgical probe, according toanother embodiment of the invention;

FIG. 40C shows detail of the distal portion of the probe of FIGS. 40A,40B;

FIGS. 41A, 41B, and 41C each show detail of the distal portion of anelectrosurgical probe, according to three different embodiments of theinvention;

FIGS. 42A and 42B schematically represent a procedure for incising andcoagulating tissue with an electrosurgical probe having a bladeelectrode, according to one embodiment of the invention;

FIG. 43A schematically represents a number of steps involved in a methodof treating a patient with an electrosurgical probe having a bladeelectrode, according to one embodiment of the invention;

FIG. 43B schematically represents a number of steps involved in a methodof concurrently severing and coagulating tissue, according to oneembodiment of the invention;

FIG. 44 schematically represents a number of steps involved in a methodof dissecting a tissue or organ of a patient with an electrosurgicalprobe, according to another embodiment of the invention;

FIGS. 45A-C each schematically represent an electrosurgical system,according to three different embodiments of the invention;

FIG. 46 is a block diagram representing an actuator unit of anelectrosurgical system of the invention;

FIG. 47 schematically represents an electrosurgical probe as seen fromthe side, the probe including at least one moveable electrode, accordingto one embodiment of the instant invention;

FIGS. 48A-E each show the distal end portion of an electrosurgical probeincluding a moveable return electrode, according to the invention;

FIGS. 49A and 49B each show the distal end portion of an electrosurgicalprobe including a return electrode having an undulating perimeter,according to one embodiment of the invention;

FIGS. 50A-C each show the distal end portion of an electrosurgical probeincluding a terminal active electrode and a moveable return electrode,according to another embodiment of the invention;

FIG. 51 shows the distal end portion of an electrosurgical probeincluding a moveable return electrode which is pivotable laterally,according to another embodiment of the invention;

FIGS. 52A and 52B each show the distal end portion of an electrosurgicalprobe including a moveable active electrode, according to anotherembodiment of the invention;

FIG. 53A schematically represents a number of steps involved in a methodof coagulating and severing a target tissue with an electrosurgicalprobe, according to one embodiment of the invention; and

FIG. 53B schematically represents a number of steps involved in a methodof modifying and ablating a target tissue, according to yet anotherembodiment of the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention provides systems and methods for selectivelyapplying electrical energy to a target location within or on a patient'sbody, particularly for cutting, ablating, clamping, and coagulating atissue using an electrosurgical probe. The instant invention alsoprovides apparatus and methods for making incisions to access a tissueor organ within a patient's body, to dissect or harvest the tissue ororgan from the patient, and to transect, resect, or otherwise modify thetissue or organ. The present invention is useful in procedures where thetarget tissue or organ is, or can be, flooded or submerged with anelectrically conductive fluid, such as isotonic saline. In addition,tissues which may be treated by the system and method of the presentinvention further include, but are not limited to, tissues of the heart,chest, knee, shoulder, ankle, hip, elbow, hand or foot; as well asprostate tissue, leiomyomas (fibroids) located within the uterus,gingival tissues and mucosal tissues located in the mouth, tumors, scartissue, myocardial tissue, collagenous tissue within the eye; togetherwith epidermal and dermal tissues on the surface of the skin. Thepresent invention is also useful for resecting tissue within accessiblesites of the body that are suitable for electrode loop resection, suchas the resection of prostate tissue, leiomyomas (fibroids) locatedwithin the uterus, or other tissue to be removed from the body.

The present invention is also useful for procedures in the head andneck, such as the ear, mouth, throat, pharynx, larynx, esophagus, nasalcavity, and sinuses. These procedures may be performed through the mouthor nose using speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, and salivaryglands, submucus resection of the nasal septum, excision of diseasedtissue and the like. In other procedures, the present invention may beuseful for cutting, resection, ablation and/or hemostasis of tissue inprocedures for treating snoring and obstructive sleep apnea (e.g., UPPPprocedures), for gross tissue removal, such as tonsillectomies,adenoidectomies, tracheal stenosis and vocal cord polyps and lesions, orfor the resection or ablation of facial tumors or tumors within themouth and pharynx, such as glossectomies, laryngectomies, acousticneuroma procedures and nasal ablation procedures. In addition, thepresent invention is useful for procedures within the ear, such asstapedotomies, tympanostomies, myringotomies, or the like.

The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention is particularly useful for ablation and sculpting of cartilagetissue, such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck region, e.g., the removal of pigmentations,vascular lesions, scars, tattoos, etc., and for other surgicalprocedures on the skin, such as tissue rejuvenation, cosmetic eyeprocedures (blepharoplasties), wrinkle removal, tightening muscles forfacelifts or browlifts, hair removal and/or transplant procedures, etc.

The present invention is also useful for harvesting blood vessels, suchas a blood vessel to be used as a graft vessel during the CABGprocedure, e.g., the saphenous vein and the internal mammary artery(IMA). One or more embodiments of the invention may be used as follows:i) to access the blood vessel to be harvested, e.g., by opening the legto access the saphenous vein, or opening the chest (either via alongitudinal incision of the sternum during an open-chest procedure, orduring a minimally invasive inter-costal procedure); ii) to dissect theblood vessel to be harvested from the surrounding connective tissuealong at least a portion of its length; and iii) to transect thedissected blood vessel at a first position only in the case of apedicled graft (IMA), or at the first position and at a second positionin the case of a free graft (saphenous vein). In each case i) to iii),as well as for other embodiment of the invention, the procedure involvesremoval of tissue by a cool ablation procedure in which a high frequencyvoltage is applied to an active electrode in the vicinity of a targettissue, typically in the presence of an electrically conductive fluid.The cool ablation procedure of the invention is described fullyelsewhere herein.

The electrically conductive fluid may be a bodily fluid such as blood orsynovial fluid, intracellular fluid of the target tissue, or isotonicsaline delivered to the target tissue during the procedure. In oneembodiment, apparatus of the invention includes a probe adapted forbeing shifted between an open configuration and a closed configuration.The present invention is useful for coagulating blood or blood vessels,for example, for coagulating blood vessels traversing a target tissueduring incising or resecting the target tissue. The present invention isalso useful for clamping a target tissue or blood vessel prior tocoagulating the tissue or blood vessel, and for severing or ablating thecoagulated tissue or blood vessel. Apparatus of the present inventionmay also be used to ablate or otherwise modify a target tissue withoutprior coagulation of the target tissue.

Although certain parts of this disclosure are directed specifically tocreating incisions for accessing a patient's thoracic cavity and theharvesting and dissection of blood vessels within the body during a CABGprocedure, systems and methods of the invention are equally applicableto other procedures involving other organs or tissues of the body,including minimally invasive procedures, other open procedures,intravascular procedures, urological procedures, laparascopy,arthroscopy, thoracoscopy or other cardiac procedures, cosmetic surgery,orthopedics, gynecology, otorhinolaryngology, spinal and neurologicprocedures, oncology, and the like.

In methods of the present invention, high frequency (RF) electricalenergy is usually applied to one or more active electrodes in thepresence of an electrically conductive fluid to remove and/or modifytarget tissue, an organ, or a body structure. Depending on the specificprocedure, the present invention may be used to: (1) create incisions intissue; (2) dissect or harvest tissue; (3) volumetrically remove tissueor cartilage (i.e., ablate or effect molecular dissociation of thetissue); (4) cut, incise, transect, or resect tissue or an organ (e.g.,a blood vessel); (5) create perforations or holes within tissue; and/or(6) coagulate blood and severed blood vessels.

In one method of the present invention, the tissue structures areincised by volumetrically removing or ablating tissue along a cuttingpath. In this procedure, a high frequency voltage difference is appliedbetween one or more active electrode (s) and one or more returnelectrode(s) to develop high electric field intensities in the vicinityof the target tissue site. The high electric field intensities lead toelectric field induced molecular breakdown of target tissue throughmolecular dissociation (rather than thermal evaporation orcarbonization). Applicant believes that the tissue structure isvolumetrically removed through molecular disintegration of largerorganic molecules into smaller molecules and/or atoms, such as hydrogen,oxides of carbon, hydrocarbons and nitrogen compounds. This moleculardisintegration completely removes the tissue structure, as opposed todehydrating the tissue material by the removal of liquid within thecells of the tissue, as is typically the case with electrosurgicaldesiccation and vaporization.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the tip of the active electrode(s) and the targettissue. The electrically conductive fluid may be a gas or liquid, suchas isotonic saline, delivered to the target site, or a viscous fluid,such as a gel, that is located at the target site. In the latterembodiment, the active electrode(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itminimizes the current flow into the electrically conductive fluid.Within the vaporized fluid a plasma is formed, and charged particles(e.g., electrons) cause the localized molecular dissociation ordisintegration of components of the target tissue, to a depth of perhapsseveral cell layers. This molecular dissociation results in thevolumetric removal of tissue from the target site. This ablationprocess, which typically subjects the target tissue to a temperature inthe range of 40° C. to 70° C., can be precisely controlled to effect theremoval of tissue to a depth as little as about 10 microns, with littleor no thermal or other damage to surrounding tissue. This cool ablationphenomenon has been termed Coblation®.

While not being bound by theory, applicant believes that the principlemechanism of tissue removal in the Coblation® mechanism of the presentinvention is energetic electrons or ions that have been energized in aplasma adjacent to the active electrode(s). When a liquid is heatedsufficiently that atoms vaporize from the liquid at a greater rate thanthey recondense, a gas is formed. When the gas is heated sufficientlythat the atoms collide with each other and electrons are removed fromthe atoms in the process, an ionized gas or plasma is formed. (A morecomplete description of plasmas (the so-called “fourth state of matter”)can be found in Plasma Physics, by R. J. Goldston and P. H. Rutherfordof the Plasma Physics Laboratory of Princeton University (1995), thecomplete disclosure of which is incorporated herein by reference.) Whenthe density of the vapor layer (or within a bubble formed in theelectrically conductive liquid) becomes sufficiently low (i.e., lessthan approximately 10²⁰ atoms/cm³ for aqueous solutions), the electronmean free path increases to enable subsequently injected electrons tocause impact ionization within these regions of low density (i.e., vaporlayers or bubbles). Once the ionic particles in the plasma layer havesufficient energy, they accelerate towards the target tissue. Energyevolved by the energetic electrons (e.g., 3.5 eV to 5 eV) cansubsequently bombard a molecule and break its bonds, dissociating amolecule into free radicals, which then combine into final gaseous orliquid species.

Plasmas may be formed by heating and ionizing a gas by driving anelectric current through it, or by transmitting radio waves into thegas. Generally, these methods of plasma formation give energy to freeelectrons in the plasma directly, and then electron-atom collisionsliberate more electrons, and the process cascades until the desireddegree of ionization is achieved. Often, the electrons carry theelectrical current or absorb the radio waves and, therefore, are hotterthan the ions. Thus, in applicant's invention, the electrons, which arecarried away from the tissue towards the return electrode, carry most ofthe plasma's heat with them, allowing the ions to break apart the tissuemolecules in a substantially non-thermal manner.

The energy evolved by the energetic electrons may be varied by adjustinga variety of factors, such as: the number of active electrodes;electrode size and spacing; electrode surface area; asperities and sharpedges on the electrode surfaces; electrode materials; applied voltageand power; current limiting means, such as inductors; electricalconductivity of the fluid in contact with the electrodes; density of thefluid; electrical insulators over the electrodes; and other factors.Accordingly, these factors can be manipulated to control the energylevel of the excited electrons. Since different tissue structures havedifferent molecular bonds, the present invention can be configured tobreak the molecular bonds of certain tissue, while having too low anenergy to break the molecular bonds of other tissue. For example, fattytissue, (e.g., adipose tissue) contains a large amount of lipid materialhaving double bonds, the breakage of which requires an energy levelsubstantially higher than 4 eV to 5 eV. Accordingly, the presentinvention can be configured such that lipid components of adipose tissueare selectively not ablated. Of course, the present invention may beused to effectively ablate cells of adipose tissue such that the innerfat content of the cells is released in a liquid form. Alternatively,the invention can be configured (e.g., by increasing the voltage orchanging the electrode configuration to increase the current density atthe electrode tips) such that the double bonds of lipid materials arereadily broken leading to molecular dissociation of lipids into lowmolecular weight condensable gases, generally as described hereinabove.A more complete description of the Coblation® phenomenon can be found incommonly assigned U.S. Pat. No. 5,683,366 and co-pending U.S. patentapplication Ser. No. 09/032,375, filed Feb. 27, 1998, the completedisclosures of which are incorporated herein by reference.

Methods of the present invention typically involve the application ofhigh frequency (RF) electrical energy to one or more active electrodesin an electrically conductive environment to remove (i.e., resect,incise, perforate, cut, or ablate) a target tissue, structure, or organ;and/or to seal one or more blood vessels within the region of the targettissue. The present invention is particularly useful for sealing largerarterial vessels, e.g., having a diameter on the order of 1 mm orgreater. In some embodiments, a high frequency power supply is providedhaving an ablation mode, wherein a first voltage is applied to an activeelectrode sufficient to effect molecular dissociation or disintegrationof the tissue; and a coagulation mode, wherein a second, lower voltageis applied to an active electrode (either the same or a differentelectrode) sufficient to achieve hemostasis of severed vessels withinthe tissue. In other embodiments, an electrosurgical probe is providedhaving one or more coagulation electrode(s) configured for sealing asevered vessel, such as an arterial vessel, and one or more activeelectrodes configured for either contracting the collagen fibers withinthe tissue or removing (ablating) the tissue, e.g., by applyingsufficient energy to the tissue to effect molecular dissociation. In thelatter embodiments, the coagulation electrode(s) may be configured suchthat a single voltage can be applied to both coagulate with thecoagulation electrode(s), and to ablate or contract tissue with theactive electrode(s). In other embodiments, the power supply is combinedwith the coagulation probe such that the coagulation electrode is usedwhen the power supply is in the coagulation mode (low voltage), and theactive electrode(s) are used when the power supply is in the ablationmode (higher voltage).

In one method of the present invention, one or more active electrodesare brought into close proximity to tissue at a target site, and thepower supply is activated in the ablation mode such that sufficientvoltage is applied between the active electrodes and the returnelectrode to volumetrically remove the tissue through moleculardissociation, as described above. During this process, vessels withinthe tissue are severed. Smaller vessels may be automatically sealed withthe system and method of the present invention. Larger vessels and thosewith a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by actuating a control (e.g., a foot pedal) toreduce the voltage of the power supply into the coagulation mode. Inthis mode, the active electrodes may be pressed against the severedvessel to provide sealing and/or coagulation of the vessel.Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed or coagulated, the surgeon may activate acontrol (e.g., another foot pedal) to increase the voltage of the powersupply back into the ablation mode. According to another aspect of theinvention, larger vessels may be clamped against the active electrodeand coagulated prior to being severed via the cool ablation process ofthe invention.

The present invention is also useful for removing or ablating tissuearound nerves, such as spinal, or cranial nerves, e.g., the hypoglossalnerve, the optic nerve, facial nerves, vestibulocochlear nerves and thelike. This is particularly advantageous when removing tissue that islocated close to nerves. One of the significant drawbacks with theconventional RF devices, scalpels, and lasers is that these devices donot differentiate between the target tissue and the surrounding nervesor bone. Therefore, the surgeon must be extremely careful during theseprocedures to avoid damage to the nerves within and around the targettissue. In the present invention, the Coblation® process for removingtissue results in no, or extremely small amounts, of collateral tissuedamage, as described above. This allows the surgeon to remove tissueclose to a nerve without causing collateral damage to the nerve fibersand surrounding tissue.

In addition to the generally precise nature of the novel mechanisms ofthe present invention, applicant has discovered an additional method ofensuring that adjacent nerves are not damaged during tissue removal.According to the present invention, systems and methods are provided fordistinguishing between the fatty tissue immediately surrounding nervefibers and the normal tissue that is to be removed during the procedure.Peripheral nerves usually comprise a connective tissue sheath, orepineurium, enclosing the bundles of nerve fibers, each bundle beingsurrounded by its own sheath of connective tissue (the perineurium) toprotect these nerve fibers. The outer protective tissue sheath orepineurium typically comprises a fatty tissue (e.g., adipose tissue)having substantially different electrical properties than the normaltarget tissue that is treated. The system of the present inventionmeasures the electrical properties of the tissue at the tip of the probewith one or more active electrode(s). These electrical properties mayinclude electrical conductivity at one, several, or a range offrequencies (e.g., in the range from 1 kHz to 100 MHz), dielectricconstant, capacitance or combinations of these. In this embodiment, anaudible signal may be produced when the sensing electrode(s) at the tipof the probe detects the fatty tissue surrounding a nerve, or directfeedback control can be provided to only supply power to the activeelectrode(s) either individually or to the complete array of electrodes,if and when the tissue encountered at the tip or working end of theprobe is normal tissue based on the measured electrical properties.

In one embodiment, the current limiting elements are configured suchthat the active electrodes will shut down or turn off when theelectrical impedance reaches a threshold level. When this thresholdlevel is set to the impedance of the fatty tissue surrounding nerves,the active electrodes will shut off whenever they come in contact with,or in close proximity to, nerves. Meanwhile, the other activeelectrodes, which are in contact with or in close proximity to targettissue, will continue to conduct electric current to the returnelectrode. This selective ablation or removal of lower impedance tissuein combination with the Coblation® mechanism of the present inventionallows the surgeon to precisely remove tissue around nerves or bone.Applicant has found that the present invention is capable ofvolumetrically removing tissue closely adjacent to nerves withoutimpairing the function of the nerves, and without significantly damagingthe tissue of the epineurium.

The present invention can be also be configured to create an incision ina bone of the patient. For example, the systems of the present inventioncan be used to create an incision in the sternum for access to thethoracic cavity. Applicant has found that the Coblation® mechanism ofthe present invention allows the surgeon to precisely create an incisionin the sternum while minimizing or preventing bone bleeding. The highfrequency voltage is applied between the active electrode(s) and thereturn electrode(s) to volumetrically remove the bone from a specificsite targeted for the incision. As the active electrode(s) are passedthrough the incision in the bone, the sides of the active electrodes (ora third coagulation electrode) slidingly contact the bone surroundingthe incision to provide hemostasis in the bone. A more completedescription of such coagulation electrodes can be found in U.S. patentapplication Ser. No. 09/162,117, filed Sep. 28, 1998, the completedisclosure of which is incorporated herein by reference.

The present invention can also be used to dissect and harvest bloodvessels from the patient's body during a CABG procedure. The system ofthe present invention allows a surgeon to dissect and harvest bloodvessels, such as the right or left IMA or saphenous vein, whileconcurrently providing hemostasis at the harvesting site. In someembodiments, a first high frequency voltage, can be delivered in anablation mode to effect molecular disintegration of connective tissueadjacent to the blood vessel targeted for harvesting; and a second,lower voltage can be delivered to achieve hemostasis of the connectivetissue adjacent to the blood vessel. In other embodiments, the targetedblood vessel can be transected at one or more positions along itslength, and one or more coagulation electrode(s) can be used to seal thetransected blood vessel at the site of transection. The coagulationelectrode(s) may be configured such that a single voltage can be appliedto the active electrodes to ablate the tissue and to coagulate the bloodvessel and target site.

The present invention also provides systems, apparatus, and methods forselectively removing tumors or other undesirable body structures whileminimizing the spread of viable cells from the tumor. Conventionaltechniques for removing such tumors generally result in the productionof smoke in the surgical setting, termed an electrosurgical or laserplume, which can spread intact, viable bacterial or viral particles fromthe tumor or lesion to the surgical team, or viable cancerous cells toother locations within the patient's body. This potential spread ofviable cells or particles has resulted in increased concerns over theproliferation of certain debilitating and fatal diseases, such ashepatitis, herpes, HIV and papillomavirus. In the present invention,high frequency voltage is applied between the active electrode(s) andone or more return electrode(s) to volumetrically remove at least aportion of the tissue cells in the tumor or lesion by the moleculardissociation of tissue components into non-condensable gases. The highfrequency voltage is preferably selected to effect controlled removal ofthese tissue cells while minimizing substantial tissue necrosis tosurrounding or underlying tissue. A more complete description of thisphenomenon can be found in co-pending U.S. patent application Ser. No.09/109,219, filed Jun. 30, 1998, the complete disclosure of which isincorporated herein by reference.

A current flow path between the active electrode(s) and the returnelectrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., within a viscous fluid, such as anelectrically conductive gel) or by directing an electrically conductivefluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry field procedure (i.e., the tissue is notsubmersed in fluid). The use of a conductive gel allows a slower, morecontrolled delivery rate of conductive fluid as compared with a liquidor a gas. In addition, the viscous nature of the gel may allow thesurgeon to more easily contain the gel around the target site (e.g., ascompared with containment of isotonic saline). A more completedescription of an exemplary method of directing electrically conductivefluid between the active and return electrodes is described in U.S. Pat.No. 5,697,281, the full disclosure of which is incorporated herein byreference. Alternatively, the body's natural conductive fluids, such asblood, may be sufficient to establish a conductive path between thereturn electrode(s) and the active electrode(s), and to provide theconditions for establishing a vapor layer, as described above. However,conductive fluid that is introduced into the patient is generallypreferred over blood because blood will tend to coagulate at certaintemperatures. Advantageously, a liquid electrically conductive fluid(e.g., isotonic saline) may be used to concurrently “bathe” the targettissue surface to provide an additional means for removing any tissue,and to cool the tissue at or adjacent to the target site.

In some embodiments of the invention, an electrosurgical probe includesan electrode support for electrically isolating the active electrode(s)from the return electrode, and a fluid delivery port or outlet fordirecting an electrically conductive fluid to the target site or to thedistal end of the probe. The electrode support and the fluid outlet maybe recessed from an outer surface of the instrument to confine theelectrically conductive fluid to the region immediately surrounding theelectrode support. In addition, a shaft of the instrument may be shapedso as to form a cavity around the electrode support and the fluidoutlet. This helps to assure that the electrically conductive fluid willremain in contact with the active electrode(s) and the returnelectrode(s) to maintain the conductive path therebetween. In addition,this will help to maintain a vapor layer and subsequent plasma layerbetween the active electrode(s) and the tissue at the treatment sitethroughout the procedure, thereby reducing any thermal damage that mightotherwise occur if the vapor layer were extinguished due to a lack ofconductive fluid. Provision of the electrically conductive fluid aroundthe target site also helps to maintain the tissue temperature at desiredlevels.

The electrically conductive fluid should have a threshold conductivityto provide a suitable conductive path between the return electrode andthe active electrode(s). The electrical conductivity of the fluid (inunits of milliSiemens per centimeter or mS/cm) will usually be greaterthan 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm.

An electrosurgical probe or instrument of the invention typicallyincludes a shaft having a proximal end and a distal end, and one or moreactive electrode(s) disposed at the shaft distal end. The shaft servesto mechanically support the active electrode(s) and permits the treatingphysician to manipulate the shaft distal end via a handle attached tothe proximal end of the shaft. The shaft may be rigid or flexible, withflexible shafts optionally being combined with a generally rigidexternal tube for mechanical support. Flexible shafts may be combinedwith pull wires, shape memory actuators, and other known mechanisms foreffecting selective deflection of the distal end of the shaft tofacilitate positioning of the electrode array. The shaft will usuallyhave one or more wires, electrode connectors, leads, or other conductiveelements running axially therethrough, to permit connection of theelectrode(s) to a connection block located at the proximal end of theinstrument. The connection block is adapted for coupling theelectrode(s) to the power supply or controller. Typically, theconnection block is housed within the handle of the probe.

The shaft of an instrument under the invention may have a variety ofdifferent shapes and sizes. Generally, the shaft will have a suitablediameter and length to allow the surgeon to access the target site withthe distal or working end of the shaft. Thus, the shaft may be providedin a range of sizes according to the particular procedure or tissuetargeted for treatment. Typically, the shaft will have a length in therange of from about 5 cm to 30 cm, and have a diameter in the range offrom about 0.5 mm to 10 mm. Specific shaft designs will be described indetail in connection with the drawings hereinafter.

The present invention may use a single active electrode or a pluralityof electrodes distributed across a contact surface of a probe (e.g., ina linear fashion). In the latter embodiment, the electrode array usuallyincludes a plurality of independently current-limited and/orpower-controlled active electrodes to apply electrical energyselectively to the target tissue while limiting the unwanted applicationof electrical energy to the surrounding tissue and environment resultingfrom power dissipation into surrounding electrically conductive liquids,such as blood, normal saline, electrically conductive gel and the like.The active electrodes may be independently current-limited by isolatingthe terminals from each other and connecting each terminal to a separatepower source that is isolated from the other active electrodes.Alternatively, the active electrodes may be connected to each other ateither the proximal or distal ends of the probe to form a single wirethat couples to a power source.

In one configuration, each individual active electrode is electricallyinsulated from all other active electrodes within the probe and isconnected to a power source which is isolated from each of the otheractive electrodes in the array, or to circuitry which limits orinterrupts current flow to the active electrode when low resistivitymaterial (e.g., blood, electrically conductive saline irrigant orelectrically conductive gel) causes a lower impedance path between thereturn electrode and the individual active electrode. The isolated powersources for each individual active electrode may be separate powersupply circuits having internal impedance characteristics which limitpower to the associated active electrode when a low impedance returnpath is encountered. By way of example, the isolated power source may bea user selectable constant current source. In this embodiment, lowerimpedance paths will automatically result in lower resistive heatinglevels since the heating is proportional to the square of the operatingcurrent times the impedance. Alternatively, a single power source may beconnected to each of the active electrodes through independentlyactuatable switches, or by independent current limiting elements, suchas inductors, capacitors, resistors and/or combinations thereof. Thecurrent limiting elements may be provided in the probe, connectors,cable, power supply or along the conductive path from the power supplyto the distal tip of the probe. Alternatively, the resistance and/orcapacitance may occur on the surface of the active electrode(s) due tooxide layers which form selected active electrodes (e.g., titanium or aresistive coating on the surface of metal, such as platinum).

The distal end of the probe may comprise many independent activeelectrodes designed to deliver electrical energy in the vicinity of thedistal end. The selective application of electrical energy to theconductive fluid is achieved by connecting each individual activeelectrode and the return electrode to a power source havingindependently controlled or current limited channels. The returnelectrode(s) may comprise a single tubular member of electricallyconductive material at the distal end of the probe proximal to theactive electrode(s) The same tubular member of electrically conductivematerial may also serve as a conduit for the supply of the electricallyconductive fluid between the active and return electrodes. Theapplication of high frequency voltage between the return electrode(s)and the active electrode(s) results in the generation of high electricfield intensities at the distal tip of the active electrode(s), withconduction of high frequency current from each active electrode to thereturn electrode. The current flow from each active electrode to thereturn electrode(s) is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the surroundingconductive fluid while minimizing energy delivery to surrounding(non-target) tissue.

The application of a suitable high frequency voltage between the returnelectrode(s) and the active electrode(s) for appropriate time intervalseffects cutting, removing, ablating, shaping, contracting or otherwisemodifying the target tissue. In one embodiment, the tissue volume overwhich energy is dissipated (i.e., over which a high current densityexists) may be precisely controlled, for example, by the use of amultiplicity of small active electrodes whose effective diameters orprincipal dimensions range from about 5 mm to 0.01 mm, preferably fromabout 2 mm to 0.05 mm, and more preferably from about 1 mm to 0.1 mm.Electrode areas for both circular and non-circular terminals will have acontact area (per active electrode) below 25 mm², preferably being inthe range from 0.0001 mm² to 1 mm², and more preferably from 0.005 mm²to 0.5 mm². The circumscribed area of the electrode array is in therange from 0.25 mm² to 75 mm², preferably from 0.5 mm² to 40 mm². In oneembodiment the probe may include a plurality of relatively small activeelectrodes disposed over the distal contact surfaces on the shaft. Theuse of small diameter active electrodes increases the electric fieldintensity and reduces the extent or depth of tissue heating as aconsequence of the divergence of current flux lines which emanate fromthe exposed surface of each active electrode.

The portion of the electrode support on which the active electrode(s)are mounted generally defines a tissue treatment surface of the probe.The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. The areaof the tissue treatment surface can range from about 0.25 mm² to 75 mm²,usually being from about 0.5 mm² to 40 mm². The geometries of the activeelectrode(s) can be planar, concave, convex, hemispherical, conical, alinear “in-line” array, or virtually any other regular or irregularshape. Most commonly, the active electrode(s) will be located at theshaft distal end of the electrosurgical probe, frequently having planar,disk-shaped, or hemispherical surfaces for use in reshaping procedures,ablating, cutting, dissecting organs, coagulating, or transecting bloodvessels. The active electrode(s) may be arranged terminally or laterallyon the electrosurgical probe (e.g., in the manner of a scalpel or ablade). However, it should be clearly understood that the activeelectrode of the invention does not cut or sever tissue mechanically asfor a scalpel blade, but rather by the localized molecular dissociationof tissue components due to application of high frequency electriccurrent to the active electrode. In one embodiment, a distal portion ofthe shaft may be flattened or compressed laterally (e.g., FIGS.32A-32C). A probe having a laterally compressed shaft may facilitateaccess to certain target sites or body structures during varioussurgical procedures.

In embodiments having a plurality of active electrodes, it should beclearly understood that the invention is not limited to electricallyisolated active electrodes. For example, a plurality of activeelectrodes may be connected to a single lead that extends through theprobe shaft and is coupled to a high frequency power supply.Alternatively, the probe may incorporate a single electrode that extendsdirectly through the probe shaft or is connected to a single lead thatextends to the power source. The active electrode may have a planar orblade shape, a screwdriver or conical shape, a sharpened point, a ballshape (e.g., for tissue vaporization and desiccation), a twizzle shape(for vaporization and needle-like cutting), a spring shape (for rapidtissue debulking and desiccation), a twisted metal shape, an annular orsolid tube shape, or the like. Alternatively, the electrode may comprisea plurality of filaments, a rigid or flexible brush electrode (fordebulking a tumor, such as a fibroid, bladder tumor or a prostateadenoma), a side-effect brush electrode on a lateral surface of theshaft, a coiled electrode, or the like.

In one embodiment, the probe comprises a single blade active electrodethat extends from an insulating support member, spacer, or electrodesupport, e.g., a ceramic or silicone rubber spacer located at the distalend of the probe. The insulating support member may be a tubularstructure or a laterally compressed structure that separates the bladeactive electrode from a tubular or annular return electrode positionedproximal to the insulating member and the active electrode. The bladeelectrode may include a distal cutting edge and sides which areconfigured to coagulate the tissue as the blade electrode advancesthrough the tissue. In yet another embodiment, the catheter or probeincludes a single active electrode that can be rotated relative to therest of the catheter body, or the entire catheter may be rotatedrelative to the electrode lead(s). The single active electrode can bepositioned adjacent the abnormal tissue and energized and rotated asappropriate to remove or modify the target tissue.

The active electrode(s) are preferably supported within or by aninsulating support member positioned near the distal end of theinstrument shaft. The return electrode may be located on the instrumentshaft, on another instrument, or on the external surface of the patient(i.e., a dispersive pad). For certain procedures, the close proximity ofnerves and other sensitive tissue makes a bipolar design more preferablebecause this minimizes the current flow through non-target tissue andsurrounding nerves. Accordingly, the return electrode is preferablyeither integrated with the instrument body, or located on anotherinstrument. The proximal end of the probe typically includes theappropriate electrical connections for coupling the return electrode(s)and the active electrode(s) to a high frequency power supply, such as anelectrosurgical generator.

One exemplary power supply of the present invention delivers a highfrequency current selectable to generate average power levels rangingfrom several milliwatts to tens of watts per electrode, depending on thevolume of target tissue being treated, and/or the maximum allowedtemperature selected for the instrument tip. The power supply allows theuser to select the voltage level according to the specific requirementsof a particular otologic procedure, neurosurgery procedure, cardiacsurgery, arthroscopic surgery, dermatological procedure, ophthalmicprocedures, open surgery or other endoscopic surgery procedure. Forcardiac procedures and potentially for neurosurgery, the power sourcemay have an additional filter, for filtering leakage voltages atfrequencies below 100 kHz, particularly voltages around 60 kHz.Alternatively, a power supply having a higher operating frequency, e.g.,300 kHz to 500 kHz may be used in certain procedures in which stray lowfrequency currents may be problematic. A description of one suitablepower supply can be found in co-pending patent application Ser. Nos.09/058,571 and 09/058,336, filed Apr. 10, 1998, the complete disclosureof both applications are incorporated herein by reference for allpurposes.

The voltage difference applied between the return electrode(s) and theactive electrode(s) will be at high or radio frequency, typicallybetween about 5 kHz and 20 MHz, usually being between about 30 kHz and2.5 MHz, preferably being between about 50 kHz and 500 kHz, often lessthan 350 kHz, and often between about 100 kHz and 200 kHz. The RMS (rootmean square) voltage applied will usually be in the range from about 5volts to 1000 volts, preferably being in the range from about 10 voltsto 500 volts depending on the active electrode size, the operatingfrequency, and the operation mode of the particular procedure or desiredeffect on the tissue (e.g., contraction, coagulation, cutting orablation). Typically, the peak-to-peak voltage for ablation or cuttingwill be in the range of 10 volts to 2000 volts and preferably in therange of 200 volts to 1800 volts, and more preferably in the range ofabout 300 volts to 1500 volts, often in the range of about 500 volts to900 volts peak to peak (again, depending on the electrode size, theoperating frequency and the operation mode). Lower peak-to-peak voltageswill be used for tissue coagulation or collagen contraction and willtypically be in the range from 50 to 1500, preferably 100 to 1000, andmore preferably 120 to 600 volts peak-to-peak.

The voltage is usually delivered in a series of voltage pulses oralternating current of time varying voltage amplitude with asufficiently high frequency (e.g., on the order of 5 kHz to 20 MHz) suchthat the voltage is effectively applied continuously (as compared withe.g., lasers claiming small depths of necrosis, which are generallypulsed about 10 Hz to 20 Hz). In addition, the duty cycle (i.e.,cumulative time in any one-second interval that energy is applied) is onthe order of about 50% for the present invention, as compared withpulsed lasers which typically have a duty cycle of about 0.0001%.

The power supply may include a fluid interlock for interrupting power tothe active electrode(s) when there is insufficient conductive fluidaround the active electrode(s). This ensures that the instrument willnot be activated when conductive fluid is not present, minimizing thetissue damage that may otherwise occur. A more complete description ofsuch a fluid interlock can be found in commonly assigned, co-pendingU.S. application Ser. No. 09/058,336, filed Apr. 10, 1998, the completedisclosure of which is incorporated herein by reference.

The power supply may also be current limited or otherwise controlled sothat undesired heating of the target tissue or surrounding (non-target)tissue does not occur. In a presently preferred embodiment of thepresent invention, current limiting inductors are placed in series witheach independent active electrode, where the inductance of the inductoris in the range of 10 uH to 50,000 uH, depending on the electricalproperties of the target tissue, the desired tissue heating rate and theoperating frequency. Alternatively, capacitor-inductor (LC) circuitstructures may be employed, as described previously in U.S. Pat. No.5,697,909, the complete disclosure of which is incorporated herein byreference. Additionally, current limiting resistors may be selected.Preferably, these resistors will have a large positive temperaturecoefficient of resistance so that, as the current level begins to risefor any individual active electrode in contact with a low resistancemedium (e.g., saline irrigant or blood), the resistance of the currentlimiting resistor increases significantly, thereby minimizing the powerdelivery from the active electrode into the low resistance medium (e.g.,saline irrigant or blood).

In some procedures, it may also be necessary to retrieve or aspirate theelectrically conductive fluid and/or the non-condensable gaseousproducts of ablation. In addition, it may be desirable to aspirate smallpieces of tissue or other body structures that are not completelydisintegrated by the high frequency energy, or other fluids at thetarget site, such as blood, mucus, purulent fluid, the gaseous productsof ablation, or the like. Accordingly, the system of the presentinvention may include one or more suction lumen(s) in the instrument, oron another instrument, coupled to a suitable vacuum source foraspirating fluids from the target site. In addition, the invention mayinclude one or more aspiration electrode(s) coupled to the distal end ofthe suction lumen for ablating, or at least reducing the volume of,non-ablated tissue fragments that are aspirated into the lumen. Theaspiration electrode(s) function mainly to inhibit clogging of the lumenthat may otherwise occur as larger tissue fragments are drawn therein.The aspiration electrode(s) may be different from the ablation activeelectrode(s), or the same electrode(s) may serve both functions. A morecomplete description of instruments incorporating aspirationelectrode(s) can be found in commonly assigned, co-pending patentapplication Ser. No. 09/010,382, filed Jan. 21, 1998, the completedisclosure of which is incorporated herein by reference.

During a surgical procedure, the distal end of the instrument and theactive electrode(s) may be maintained at a small distance away from thetarget tissue surface. This small spacing allows for the continuous flowof electrically conductive fluid into the interface between the activeelectrode(s) and the target tissue surface. The continuous flow of theelectrically conductive fluid helps to ensure that the thin vapor layerwill remain between the active electrode(s) and the tissue surface. Inaddition, dynamic movement of the active electrode(s) over the tissuesite allows the electrically conductive fluid to cool the tissueunderlying and surrounding the target tissue to minimize thermal damageto this surrounding and underlying tissue. Accordingly, the electricallyconductive fluid may be cooled to facilitate the cooling of the tissue.Typically, the active electrode(s) will be about 0.02 mm to 2 mm fromthe target tissue and preferably about 0.05 mm to 0.5 mm during theablation process. One method of maintaining this space is to move,translate and/or rotate the probe transversely relative to the tissue,i.e., for the operator to use a light brushing motion, to maintain athin vaporized layer or region between the active electrode and thetissue. Of course, if coagulation or collagen shrinkage of a deeperregion of tissue is necessary (e.g., for sealing a bleeding vesselembedded within the tissue), it may be desirable to press the activeelectrode(s) against the tissue to effect joulean heating therein.

Referring to FIG. 1, an exemplary electrosurgical system 11 for cutting,ablating, resecting, or otherwise modifying tissue will now be describedin detail. Electrosurgical system 11 generally comprises anelectrosurgical handpiece or probe 10 connected to a power supply 28 forproviding high frequency voltage to a target site, and a fluid source 21for supplying electrically conductive fluid 50 to probe 10. In addition,electrosurgical system 11 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site. The endoscope maybe integral with probe 10, or it may be part of a separate instrument.The system 11 may also include a vacuum source (not shown) for couplingto a suction lumen or tube 211 (see FIG. 2) in the probe 10 foraspirating the target site.

As shown, probe 10 generally includes a proximal handle 19 and anelongate shaft 18 having one or more active electrodes 58 at its distalend. A connecting cable 34 has a connector 26 for electrically couplingthe active electrodes 58 to power supply 28. In embodiments having aplurality of active electrodes, active electrodes 58 are electricallyisolated from each other and the terminal of each active electrode 58 isconnected to an active or passive control network within power supply 28by means of a plurality of individually insulated conductors (notshown). A fluid supply tube 15 is connected to a fluid tube 14 of probe10 for supplying electrically conductive fluid 50 to the target site.

Power supply 28 has an operator controllable voltage level adjustment 30to change the applied voltage level, which is observable at a voltagelevel display 32. Power supply 28 also includes first, second, and thirdfoot pedals 37, 38, 39 and a cable 36 which is removably coupled topower supply 28. The foot pedals 37, 38, 39 allow the surgeon toremotely adjust the energy level applied to active electrode(s) 58. Inan exemplary embodiment, first foot pedal 37 is used to place the powersupply into the “ablation” mode and second foot pedal 38 places powersupply 28 into the “coagulation” mode. The third foot pedal 39 allowsthe user to adjust the voltage level within the ablation mode. In theablation mode, a sufficient voltage is applied to the active electrodesto establish the requisite conditions for molecular dissociation of thetissue (i.e., vaporizing a portion of the electrically conductive fluid,ionizing the vapor layer and accelerating charged particles against thetissue). As discussed above, the requisite voltage level for ablationwill vary depending on the number, size, shape and spacing of theelectrodes, the distance in which the electrodes extend from the supportmember, etc. When the surgeon is using the power supply in the ablationmode, voltage level adjustment 30 or third foot pedal 39 may be used toadjust the voltage level to adjust the degree or aggressiveness of theablation.

Of course, it will be recognized that the voltage and modality of thepower supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient means forcontrolling the power supply while manipulating the probe during asurgical procedure.

In the coagulation mode, the power supply 28 applies a low enoughvoltage to the active electrode(s) (or the coagulation electrode) toavoid vaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternately stepping on foot pedals 37, 38, respectively. This allowsthe surgeon to quickly move between coagulation and ablation in situ,without having to remove his/her concentration from the surgical fieldor without having to request an assistant to switch the power supply. Byway of example, as the surgeon is sculpting soft tissue in the ablationmode, the probe typically will simultaneously seal and/or coagulatesmall severed vessels within the tissue. However, larger vessels, orvessels with high fluid pressures (e.g., arterial vessels) may not besealed in the ablation mode. Accordingly, the surgeon can simply step onfoot pedal 38, automatically lowering the voltage level below thethreshold level for ablation, and apply sufficient pressure onto thesevered vessel for a sufficient period of time to seal and/or coagulatethe vessel. After this is completed, the surgeon may quickly move backinto the ablation mode by stepping on foot pedal 37. A specific designof a suitable power supply for use with the present invention can befound in Provisional Patent Application No. 60/062,997, filed Oct. 23,1997, the contents of which are incorporated herein by reference intheir entirety.

FIG. 2 shows an electrosurgical probe 20 according to one embodiment ofthe invention. Probe 20 may be used in conjunction with a system similaror analogous to system 11 (FIG. 1). As shown in FIG. 2, probe 20generally includes an elongated shaft 100 which may be flexible orrigid, a handle 204 coupled to the proximal end of shaft 100 and anelectrode support member 102 coupled to the distal end of shaft 100.Shaft 100 may comprise a plastic material that is easily molded into theshape shown in FIG. 3, or shaft 100 may comprise an electricallyconductive material, usually a metal, such as tungsten, stainless steelalloys, platinum or its alloys, titanium or its alloys, molybdenum orits alloys, and nickel or its alloys. In the latter case (i.e., shaft100 is electrically conductive), probe 20 includes an electricallyinsulating jacket 108, which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision ofelectrically insulating jacket 108 over shaft 100 prevents directelectrical contact between the metal shaft and any adjacent bodystructure or the surgeon. Such direct electrical contact between a bodystructure (e.g., heart, bone, nerves, skin, or other blood vessels) andan exposed electrode could result in unwanted heating and necrosis ofthe structure at the point of contact.

Handle 204 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. Handle 204 defines aninner cavity (not shown) that houses an electrical connections unit 250(FIG. 5), and provides a suitable interface for coupling probe 20 topower supply 28 via an electrical connecting cable. Electrode supportmember 102 extends from the distal end of shaft 100 (usually about 1 mmto 20 mm), and provides support for an active electrode or a pluralityof electrically isolated active electrodes 104. In the specificconfiguration shown in FIG. 2, probe 20 includes a plurality of activeelectrodes. As shown in FIG. 2, a fluid tube 233 extends through anopening in handle 204, and includes a connector 235 for connection to afluid supply source for supplying electrically conductive fluid to thetarget site. Fluid tube 233 is coupled to a distal fluid tube 239 thatextends along the outer surface of shaft 100 to an opening 237 at thedistal end of the probe 20, as will be discussed in detail below. Ofcourse, the invention is not limited to this configuration. For example,fluid tube 233 may extend through a single lumen (not shown) in shaft100, it may be coupled to a plurality of lumens (also not shown) thatextend through shaft 100 to a plurality of openings at its distal end,or the fluid tube may be completely independent of shaft 100. Probe 20may also include a valve or equivalent structure for controlling theflow rate of the electrically conductive fluid to the target site.

As shown in FIGS. 3 and 4, electrode support member 102 has asubstantially planar tissue treatment surface 212 and comprises asuitable insulating material (e.g., a ceramic or glass material, such asalumina, zirconia and the like) which could be formed at the time ofmanufacture in a flat, hemispherical or other shape according to therequirements of a particular procedure. The preferred support membermaterial is alumina (Kyocera Industrial Ceramics Corporation, Elkgrove,Ill.), because of its high thermal conductivity, good electricallyinsulative properties, high flexural modulus, resistance to carbontracking, biocompatibility, and high melting point. Electrode supportmember 102 is adhesively joined to a tubular support member (not shown)that extends most or all of the distance between support member 102 andthe proximal end of probe 20. The tubular member preferably comprises anelectrically insulating material, such as an epoxy or silicone-basedmaterial.

In a preferred construction technique, active electrodes 104 extendthrough pre-formed openings in the support member 102 so that theyprotrude above tissue treatment surface 212 by the desired distance. Theelectrodes are then bonded to the tissue treatment surface 212 ofsupport member 102, typically by an inorganic sealing material. Thesealing material is selected to provide effective electrical insulation,and good adhesion to both support member 102 and active electrodes 104.In one embodiment, active electrodes 104 comprise an electricallyconducting, corrosion resistant metal, such as platinum or titanium. Thesealing material additionally should have a compatible thermal expansioncoefficient and a melting point well below that of platinum or titaniumand alumina or zirconia, typically being a glass or glass ceramic.

In the embodiment shown in FIGS. 2-5, probe 20 includes a returnelectrode 112 for completing the current path between active electrodes104 and a high frequency power supply 28 (see FIG. 1). As shown, returnelectrode 112 preferably comprises an annular conductive band coupled tothe distal end of shaft 100 at a location proximal to tissue treatmentsurface 212 of electrode support member 102, typically about 0.5 mm to10 mm proximal to surface 212, and more preferably about 1 mm to 10 mmproximal to surface 212. Return electrode 112 is coupled to a connector258 that extends to the proximal end of probe 20, where it is suitablyconnected to power supply 28 (FIGS. 1 and 2).

As shown in FIG. 2, return electrode 112 is not directly connected toactive electrodes 104. To complete this current path so that activeelectrodes 104 are electrically connected to return electrode 112,electrically conductive fluid (e.g., isotonic saline) is caused to flowtherebetween. In the representative embodiment, the electricallyconductive fluid is delivered through an external fluid tube 239 toopening 237, as described above (FIGS. 2 and 4). Alternatively, thefluid may be continuously delivered by a fluid delivery element (notshown) that is separate from probe 20.

In alternative embodiments, the fluid path may be formed in probe 20 by,for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 100 (not shown).This annular gap may be formed near the perimeter of the shaft 100 suchthat the electrically conductive fluid tends to flow radially inwardtowards the target site, or it may be formed towards the center of shaft100 so that the fluid flows radially outward. In both of theseembodiments, a fluid source (e.g., a bag of fluid elevated above thesurgical site or having a pumping device), is coupled to probe 20 via afluid supply tube (not shown) that may or may not have a controllablevalve. A more complete description of an electrosurgical probeincorporating one or more fluid lumen(s) can be found in U.S. Pat. No.5,697,281, filed on Jun. 7, 1995, the complete disclosure of which isincorporated herein by reference.

Referring to FIGS. 3 and 4, the electrically isolated active electrodes104 are preferably spaced from each other and aligned to form a lineararray 105 of electrodes for cutting a substantially linear incision inthe tissue. The tissue treatment surface and individual activeelectrodes 104 will usually have dimensions within the ranges set forthabove. Active electrodes 104 preferably have a distal edge 107 toincrease the electric field intensities around terminals 104, and tofacilitate cutting of tissue. Thus, active electrodes 104 have ascrewdriver shape in the representative embodiment of FIGS. 2-4. In onerepresentative embodiment, the tissue treatment surface 212 has acircular cross-sectional shape with a diameter in the range of about 1mm to 30 mm, usually about 2 mm to 20 mm. The individual activeelectrodes 104 preferably extend outward from tissue treatment surface212 by a distance of about 0.1 mm to 8 mm, usually about 1 mm to 4 mm.Applicant has found that this configuration increases the high electricfield intensities and associated current densities around activeelectrodes 104 to facilitate the ablation of tissue as described indetail above.

Probe 20 may include a suction or aspiration lumen 213 (see FIG. 2)within shaft 100 and a suction tube 211 (FIG. 2) for aspirating tissue,fluids and/or gases from the target site. In this embodiment, theelectrically conductive fluid generally flows from opening 237 of fluidtube 239 radially inward and then back through one or more openings (notshown) in support member 102. Aspirating the electrically conductivefluid during surgery allows the surgeon to see the target site, and itprevents the fluid from flowing into the patient's body (e.g., thethoracic cavity). This aspiration should be controlled, however, so thatthe conductive fluid maintains a conductive path between the activeelectrode(s) and the return electrode. In some embodiments, the probe 20will also include one or more aspiration electrode(s) (not shown)coupled to the aspiration lumen for inhibiting clogging duringaspiration of tissue fragments from the surgical site. A more completedescription of these embodiments can be found in commonly assignedco-pending U.S. patent application Ser. No. 09/010,382, filed Jan. 21,1998, the complete disclosure of which is incorporated herein byreference for all purposes.

FIG. 5 illustrates the electrical connections 250 within handle 204 forcoupling active electrodes 104 and return electrode 112 to the powersupply 28. As shown, a plurality of wires 252 extend through shaft 100to couple electrodes 104 to a plurality of pins 254, which are pluggedinto a connector block 256 for coupling to a connecting cable 22 (FIG.1). Similarly, return electrode 112 is coupled to connector block 256via a wire 258 and a plug 260.

According to the present invention, probe 20 further includes anidentification element that is characteristic of the particularelectrode assembly so that the same power supply 28 can be used fordifferent electrosurgical operations. In one embodiment, for example,probe 20 includes a voltage reduction element or a voltage reductioncircuit for reducing the voltage applied between the active electrodes104 and the return electrode 112. The voltage reduction element servesto reduce the voltage applied by the power supply so that the voltagebetween the active electrodes and the return electrode is low enough toavoid excessive power dissipation into the electrically conductivemedium and/or the tissue at the target site. The voltage reductionelement primarily allows the electrosurgical probe 10/20 to becompatible with a range of different power supplies that are adapted toapply higher voltages for ablation or vaporization of tissue (e.g.,various power supplies or generators manufactured by ArthroCareCorporation, Sunnyvale, Calif.). For contraction of tissue, for example,the voltage reduction element will serve to reduce a voltage of about100 to 135 volts RMS (which corresponds to a setting of 1 on theArthroCare Model 970 and 980 (i.e., 2000) Generators) to about 45 to 60volts RMS, which is a suitable voltage for contraction of tissue withoutablation (e.g., molecular dissociation) of the tissue.

Again with reference to FIG. 5, n the representative embodiment thevoltage reduction element is a dropping capacitor 262 which has a firstleg 264 coupled to the return electrode wire 258 and a second leg 266coupled to connector block 256. Of course, the capacitor may be locatedin other places within the system, such as in, or distributed along thelength of, the cable, the power supply, the connector, etc. In addition,it will be recognized that other voltage reduction elements, such asdiodes, transistors, inductors, resistors, capacitors or combinationsthereof, may be used in conjunction with the present invention. Forexample, probe 20 may include a coded resistor (not shown) that isconstructed to lower the voltage applied between return electrode 112and active electrodes 104 to a suitable level for contraction of tissue.In addition, electrical circuits may be employed for this purpose.

Alternatively or additionally, the cable 22 that couples the powersupply 28 to probe 10/20 may be used as a voltage reduction element. Thecable has an inherent capacitance that can be used to reduce the powersupply voltage if the cable is placed into the electrical circuitbetween the power supply, the active electrodes and the returnelectrode. In this embodiment, the cable 22 may be used alone, or incombination with one of the voltage reduction elements discussed above,e.g., a capacitor.

Further, it should be noted that various electrosurgical probes of thepresent invention can be used with a particular power supply that isadapted to apply a voltage within a selected range for a certainprocedure or treatment. In which case, a voltage reduction element orcircuitry may not be necessary nor desired.

With reference to FIGS. 6-8, electrode support member 70 according toone embodiment includes a multi-layer substrate comprising a suitablehigh temperature, electrically insulating material, such as ceramic. Themulti-layer substrate is a thin or thick-film hybrid having conductivestrips that are adhered to the ceramic wafer layers (e.g., thick-filmprinted and fired onto or plated onto the ceramic wafers). Theconductive strips typically comprise tungsten, gold, nickel, silver,platinum or equivalent materials. In the exemplary embodiment, theconductive strips comprise tungsten, and they are co-fired together withthe wafer layers to form an integral package. The conductive strips arecoupled to external wire connectors by holes or vias that are drilledthrough the ceramic layers, and plated or otherwise covered withconductive material. A more complete description of such support members370 can be found in U.S. patent application Ser. No. 08/977,845, filedNov. 25, 1997, the entire disclosure of which is incorporated herein byreference.

In the representative embodiment, support member 70 comprises fiveceramic layers 200, 202, 204, 206, 208 (see FIGS. 6-10), three goldplated active electrodes 210 a, 210 b, 210 c and first and second goldplated return electrodes 216, 218. As shown in FIGS. 9A and 9B, a firstceramic layer 200, which is one of the outer layers of support 70,includes first gold plated return electrode 216 on a lateral surface 220of layer 200. First ceramic layer 200 further includes a gold conductivestrip 222 extending from return electrode 216 to the proximal end oflayer 200 for coupling to a lead wire (not shown), and three goldconductive lines 224, 226, 228 extending from a mid-portion of layer 200to its proximal end. Conductive strips 224, 226, 228 are each coupled toone of the active electrodes 210 a, 210 b, 210 c by conductive holes orvias 230, 232, 234, respectively. As shown, all three vias 230, 232, 234extend through wafer layer 200.

Referring to FIGS. 10A and 10B, a second wafer layer 202 is bondedbetween first outer wafer layer 200 and a middle wafer layer 204 (SeeFIGS. 11A and 11B). As shown, first active electrode 210 a is attachedto the distal surface of second wafer layer 202, and a conductive strip240 extends to via 230 to couple active electrode 210 a to a lead wire.Similarly, wafer layers 204 and 206 (FIGS. 11A, 11B, 12A, and 12B) eachhave an active electrode 210 b, 210 c plated to their distal surfaces,and a conductive strip 242, 244, respectively, extending to one of thevias 232, 234, respectively. Note that the vias only extend as far asnecessary through the ceramic layers. As shown in FIG. 13, a secondouter wafer layer 208 has a second return electrode 218 plated to thelateral surface 250 of layer 208. The second return electrode 218 iscoupled directly to the first return electrode 216 through a via 252extending through the entire ceramic substrate.

Of course, it will be recognized that a variety of different types ofsingle layer and multi-layer wafers may be constructed according to thepresent invention. For example, FIGS. 14 and 15 illustrate analternative embodiment of the multi-layer ceramic wafer, wherein theactive electrodes comprise planar strips 280 that are plated orotherwise bonded between the ceramic wafer layers 282. Each of theplanar strips 280 has a different length, as shown in FIG. 15, so thatthe active electrodes can be electrically isolated from each other, andcoupled to lead wires by vias (not shown).

FIG. 16 illustrates an electrosurgical probe 20′ according to anotherembodiment of the present invention. Probe 20′ generally includes handle104 attached to shaft 100, and has a single, thin, elongated activeblade electrode 58. Active electrode 58 is mechanically and electricallyseparated from return electrode 112 by a support structure 102. Theactive blade electrode 58 has a sharp distal edge 59 which helpsfacilitate the cutting process, and sides 62 which contact the tissue(e.g., bone) as the blade electrode 58 passes through the tissue or bodystructure. By contacting the sides of the blade electrode 58 directlywith the tissue or body structure, the electrical power supplied toelectrode 58 by power supply 28 can provide hemostasis to the bodystructure during the cutting process. Optionally, probe 20′ can furtherinclude one or more coagulation electrode(s) (not shown) configured toseal a severed vessel, bone, or other tissue that is being incised. Suchcoagulation electrode(s) may be configured such that a single voltagecan be applied to coagulate with the coagulation electrode(s) whileablating tissue with the active electrode(s). According to one aspect ofthe invention, probe 20′ is particularly useful for creating an incisionin a patient's chest. For example, in an open-chest CABG procedure amedian sternotomy is first performed in which the sternum is sectionedlongitudinally so as to allow the chest to be opened for access to thethoracic cavity. Active electrodes 58 include distal edge 59 suitablefor sectioning the sternum, and sides 62 suitable for arresting bonebleeding within the incised sternum. Sides 62 are configured to slidablyengage the sternum as active electrode 58 is moved with respect to thesternum. Return electrode 112 is spaced proximally from active electrode58 such that the electrical current is drawn away from the surroundingtissue. Alternatively, the return electrode 112 may be a dispersive padlocated on the external surface of the patient's body. By minimizingbleeding of the sternum during an open-chest procedure, the patient'srecovery time can be substantially shortened and patient suffering isalleviated.

FIGS. 17A-17C schematically illustrate the distal portion of threedifferent embodiments of a probe 90 according to the present invention.As shown in FIG. 17A, active electrodes 104 are anchored in a support102 of suitable insulating material (e.g., ceramic or glass material,such as alumina, zirconia and the like) which could be formed at thetime of manufacture in a flat, hemispherical or other shape according tothe requirements of a particular procedure. In one embodiment, thesupport material is alumina, available from Kyocera Industrial CeramicsCorporation, Elkgrove, Ill., because of its high thermal conductivity,good electrically insulative properties, high flexural modulus,resistance to carbon tracking, biocompatibility, and high melting point.The support 102 is adhesively joined to a tubular support member 78 thatextends most or all of the distance between matrix 102 and the proximalend of probe 90. Tubular member 78 preferably comprises an electricallyinsulating material, such as an epoxy or silicone-based material.

According to one construction technique, active electrodes 104 extendthrough pre-formed openings in the support 102 so that they protrudeabove tissue treatment surface 212 by the desired distance. Theelectrodes are then bonded to the tissue treatment surface 212 ofsupport 102, typically by an inorganic sealing material 80. Sealingmaterial 80 is selected to provide effective electrical insulation, andgood adhesion to both the support 102 and the platinum or titaniumactive electrodes. Sealing material 80 additionally should have acompatible thermal expansion coefficient, and a melting point well belowthat of platinum or titanium and alumina or zirconia, typically being aglass or glass ceramic.

In the embodiment shown in FIG. 17A, return electrode 112 comprises anannular member positioned around the exterior of shaft 100 of probe 90.Return electrode 112 may fully or partially circumscribe tubular member78 to form an annular gap 54 therebetween for flow of electricallyconductive liquid 50 therethrough, as discussed below. Gap 54 preferablyhas a width in the range of 0.25 mm to 4 mm. Alternatively, probe 90 mayinclude a plurality of longitudinal ribs between tubular member 78 andreturn electrode 112 to form a plurality of fluid lumens extending alongthe perimeter of shaft 100. In this embodiment, the plurality of lumenswill extend to a plurality of openings.

Return electrode 112 is disposed within an electrically insulativejacket 17, which is typically formed as one or more electricallyinsulative sheaths or coatings, such as polytetrafluoroethylene,polyimide, and the like. The provision of the electrically insulativejacket 17 over return electrode 112 prevents direct electrical contactbetween return electrode 112 and any adjacent body structure. Suchdirect electrical contact between a body structure (e.g., the heart) andan exposed electrode member 112 could result in unwanted heating andnecrosis of the structure at the point of contact.

As shown in FIG. 17A, return electrode 112 is not directly connected toactive electrodes 104. To complete a current path so that activeelectrodes 104 are electrically connected to return electrode 112,electrically conductive liquid 50 (e.g., isotonic saline) is caused toflow along fluid path(s) 83. Fluid path 83 is formed by annular gap 54between outer return electrode 112 and tubular support member 78. Theelectrically conductive liquid 50 flowing through fluid path 83 providesa pathway for electrical current flow between active electrodes 104 andreturn electrode 112, as illustrated by the current flux lines 60 inFIG. 17A. When a voltage difference is applied between active electrodes104 and return electrode 112, high electric field intensities will begenerated at the distal tips of active electrodes 104 with current flowfrom electrodes 104 through the target tissue to the return electrode,the high electric field intensities causing ablation of tissue 52 inzone 88.

FIG. 17B illustrates another alternative embodiment of electrosurgicalprobe 90 which has a return electrode 112 positioned within tubularmember 78. Return electrode 112 may comprise a tubular member definingan inner lumen 57 for allowing electrically conductive liquid 50 (e.g.,isotonic saline) to flow therethrough in electrical contact with returnelectrode 112. In this embodiment, a voltage difference is appliedbetween active electrodes 104 and return electrode 112 resulting inelectrical current flow through the electrically conductive liquid 50 asshown by current flux lines 60. As a result of the applied voltagedifference and concomitant high electric field intensities at the tipsof active electrodes 104, tissue 52 becomes ablated or transected inzone 88.

FIG. 17C illustrates another embodiment of probe 90 that is acombination of the embodiments in FIGS. 17A and 17B. As shown, thisprobe includes both an inner lumen 57 and an outer gap or plurality ofouter lumens 54 for flow of electrically conductive fluid. In thisembodiment, the return electrode 112 may be positioned within tubularmember 78 as in FIG. 17B, outside of tubular member 78 as in FIG. 17A,or in both locations.

FIG. 18 illustrates another embodiment of probe 90 where the distalportion of shaft 100 is bent so that active electrodes extendtransversely to the shaft. Preferably, the distal portion of shaft 100is perpendicular to the rest of the shaft so that tissue treatmentsurface 212 is generally parallel to the shaft axis. In this embodiment,return electrode 112 is mounted to the outer surface of shaft 100 and iscovered with an electrically insulating jacket 17. The electricallyconductive fluid 50 flows along flow path 83 through return electrode112 and exits the distal end of electrode 112 at a point proximal oftissue treatment surface 212. The fluid is directed exterior of shaft tosurface 212 to create a return current path from active electrodes 104,through the fluid 50, to return electrode 112, as shown by current fluxlines 60.

FIG. 19 illustrates another embodiment of the invention whereelectrosurgical system 11 further includes a liquid supply instrument 64for supplying electrically conductive fluid 50 between active electrodes104 and a return electrode 112′. Liquid supply instrument 64 comprisesan inner tubular member or return electrode 112′ surrounded by anelectrically insulating jacket 17. Return electrode 112′ defines aninner passage 83 for flow of fluid 50. As shown in FIG. 19, the distalportion of instrument 64 is preferably bent so that liquid 50 isdischarged at an angle with respect to instrument 64. This allows thesurgical team to position liquid supply instrument 64 adjacent tissuetreatment surface 212 with the proximal portion of supply instrument 64oriented at a similar angle to probe 90.

The present invention is not limited to an electrode array disposed on arelatively planar surface at the distal tip of probe 90, as describedabove. Referring to FIGS. 20A and 20B, an alternative probe 90 includesa pair of electrodes 105 a, 105 b mounted to the distal end of shaft100. Electrodes 105 a, 105 b are electrically connected to a powersupply, as described above, and preferably have tips 107 a, 107 b havinga screwdriver shape. The screwdriver shape provides a greater amount of“edges” to electrodes 105 a, 105 b, to increase the electric fieldintensity and current density at tips 107 a, 107 b, thereby improvingthe cutting ability as well as the ability to provide hemostasis of theincised tissue.

FIG. 21 illustrates yet another embodiment designed for cutting of bodytissue, organs, or structures. In this embodiment, the active electrodes104 are arranged in a linear or columnar array of one of more closelyspaced columns so that as the electrodes 104 are moved along the longeraxis (denoted by arrow 160 in FIG. 21), the current flux lines arenarrowly confined at the tip of the active electrodes 104 and result ina cutting effect in the body structure being treated. As before, thecurrent flux lines 60 emanating from the active electrodes 104 passthrough the electrically conductive liquid to the return electrodestructure 112 located proximal to the probe tip.

Referring now to FIGS. 22 and 23, alternative geometries are shown forthe active electrodes 104. These alternative electrode geometries allowthe electrical current densities emanating from the active electrodes104 to be concentrated to achieve an increased ablation rate and/or amore concentrated ablation effect due to the fact that sharper edges(i.e., regions of smaller radii of curvature) result in higher currentdensities. FIG. 22 illustrates a flattened extension of a round wireactive electrode 104 which results in higher current densities at theedges 180. Another example is shown in FIG. 23 in which the activeelectrode 104 is formed into a cone shaped point 182 resulting in highercurrent densities at the tip of the cone.

Another embodiment of the electrosurgical probe is illustrated in FIG.24. The electrosurgical probe 90 comprises a shaft 100 and at least twoactive electrodes 104 extending from a support 102 at the distal end ofthe shaft. The active electrodes 104 preferably define a distal edge 600for making an incision in tissue. The edges 600 of the active electrodes104 are substantially parallel with each other and usually spaced adistance of about 4 mm to 15 mm apart, preferably about 8 mm to 10 mmapart. The edges 600 extend from the distal end of support 102 by adistance of about 0.5 mm to 10 mm, preferably about 2 mm to 5 mm. In theexemplary embodiment, probe 90 will include a return electrode 112spaced proximally from the active electrodes 104. In an alternativeembodiment (not shown), one of the active electrodes 104 may function asa return electrode, or the return electrode may be a dispersive padlocated on an external surface of the patient's body.

FIG. 25 illustrates a distal portion of an electrosurgical probe 500according to another embodiment of the present invention The embodimentof FIG. 25 is particularly useful for cutting or creating incisions intissue structures. Probe 500 comprises a support member 502 coupled to ashaft or disposable tip (not shown) as described in previousembodiments. Support member 502 preferably comprises an inorganicelectrically insulating material, such as ceramic, glass orglass-ceramic. In this embodiment, however, support member 502 maycomprise an organic material, such as plastic, because the activeelectrode 506 and return electrode 508 are both spaced away from supportmember 502. Thus, the high intensity electric fields may be far enoughaway from support member 502 so as to allow an organic material.

An electrode assembly 504 extends from a distal end of support member502, preferably by a distance of about 2 mm to 20 mm. Electrode assembly504 comprises a single, active electrode 506 and a return electrodesleeve 508 spaced proximally from active electrode 506 by an insulationmember 510, which preferably comprises an inorganic material, such asceramic, glass or glass-ceramic. As shown, active electrode 506preferably tapers to a sharp distal end 512 to facilitate the cutting orincising of tissue. In the exemplary embodiment, active electrode 506has a proximal diameter of about 0.2 to 20 mm and a distal diameter ofless than about 0.2 mm. Return electrode 508 is spaced from activeelectrode 506 a sufficient distance to prevent shorting or arcingtherebetween at sufficient voltages to allow the volumetric removal oftissue. In the representative embodiment, the distal exposed portion ofreturn electrode 508 is spaced about 0.5 to about 5 mm from the proximalexposed portion of active electrode 506. Of course, it will berecognized that the present invention is not limited to the particulardimensions and configuration of the electrode assembly 504 describedherein, and a variety of different configurations may be envisioneddepending on the surgical application.

As shown, probe 500 includes a fluid lumen 520 passing through supportmember 502 to a distal opening (not shown) at the distal end of supportmember 502. Fluid lumen 520 is coupled to a supply of electricallyconductive fluid, such as isotonic saline, or other suitable conductivefluid for delivery of such fluid to the target site. In the exemplaryembodiment, probe 500 is designed such that lumen 520 will be positionedabove electrode assembly 504 during use such that the conductive fluidexiting the distal opening of lumen 520 will naturally pass over returnelectrode 508 and active electrode 506 thereby creating a current paththerebetween. In addition, the conductive fluid will be sufficient tocover the active electrode 506 such that the conditions for plasmaformation can be met, as described in detail above.

FIGS. 26, and 27A-C illustrate another exemplary electrosurgical probe310 for cutting, incising, or removing tissue structures. Probe 310comprises a shaft or disposable tip 313 removably coupled to a proximalhandle 312, and an electrically insulating electrode support member 370extending from tip 313 for supporting a plurality of active electrodes358. Tip 313 and handle 312 typically comprise a plastic material thatis easily molded into a suitable shape for handling by the surgeon. Asshown in FIGS. 27A and 27B, handle 312 defines an inner cavity 372 thathouses the electrical connections 374, and provides a suitable interfacefor connection to electrical connecting cable 22 (see FIG. 1). In theexemplary embodiment, handle 312 is constructed of a steam autoclavableplastic or metal (e.g., polyethylether ketone, or a stable metal alloycontaining aluminum and/or zinc) so that it can be re-used bysterilizing handle 312 between surgical procedures. High servicetemperature materials are preferred, such as a silicone cable jacket anda polyetherimide handpiece or ULTEM® that can withstand repeatedexposure to high temperatures.

Referring to FIGS. 27A-27C, tip 313 preferably comprises first andsecond housing halves 500, 502 that snap fit together, and form a recess404 therebetween for holding electrode support member 370 within the tip313. Electrode support member 370 extends from the distal end of tip313, usually by about 0.5 mm to 20 mm, and provides support for aplurality of electrically isolated active electrodes 358 and one or morereturn electrodes 400. Alternatively, electrode support member 370 maybe recessed from the distal end of tip 313 to help confine theelectrically conductive fluid around the active electrodes 358 duringthe surgical procedure, as discussed above. Electrode support member 370has a substantially planar tissue treatment surface 380 that is usuallydisposed at an angle of about 10 to 90 degrees relative to thelongitudinal axis of handle 312 to facilitate handling by the surgeon.In the exemplary embodiment, this function is accomplished by orientingtip 313 at an acute angle relative to the longitudinal axis of handle312.

In the embodiment shown in FIGS. 26-27C, probe 310 includes a singleannular return electrode 400 for completing the current path betweenactive electrodes 358 and power supply 28 (see FIG. 1). As shown, returnelectrode 400 preferably has a fluid contact surface slightly proximalto tissue treatment surface 380, typically by about 0.1 mm to 2 mm, andpreferably by about 0.2 mm to 1 mm. Return electrode 400 is coupled to aconnector 404 that extends to the proximal end of handle 313, where itis suitably connected to power supply 28 (FIG. 1).

Referring again to FIGS. 27A-27C, tip 313 further includes a proximalhub 506 for supporting a male electrical connector 508 that holds aplurality of wires 510 each coupled to one of the active electrodes 358or to return electrode 400 on support member 370. A female connector 520housed within handle 312 is removably coupled to male connector 508, anda plurality of wires 522 extend from female connector 520 through astrain relief 524 to cable 334. Both sets of wires 510, 522 areinsulated to prevent shorting in the event of fluid ingress into theprobe 310. This design allows for removable connection of the electrodesin tip 313 with the connector 520 within handle 312 so that the handlecan be re-used with different tips 313. Probe 310 will preferably alsoinclude an identification element, such as a coded resistor (not shown),for programming a particular voltage output range and mode of operationfor the power supply. This allows the power supply to be employed with avariety of different probes for a variety of different applications.

In the representative embodiment, probe 310 includes a fluid tube 410(FIG. 26) for delivering electrically conductive fluid to the targetsite. Fluid tube 410 is sized to extend through a groove 414 in handle313 and through an inner cavity 412 in tip 312 to a distal opening 414(FIG. 26) located adjacent electrode support member 370. Tube 410extends all the way through inner cavity 412 to opening 414 to eliminateany possible fluid ingress into cavity 412. Fluid tube 410 includes aproximal connector for coupling to an electrically conductive fluidsource 321.

Probe 310 will also include a valve or equivalent structure forcontrolling the flow rate of the electrically conductive fluid to thetarget site. In the representative embodiment shown in FIGS. 27A-27C,handle 312 comprises a main body 422 coupled between distal hub 418 andstrain relief 420, and a rotatable sleeve 416 around main body 422.Distal hub 418 has an opening 419 for receiving proximal hub 506 of tip313 for removably coupling the tip 313 to the handle 312. Sleeve 416 isrotatably coupled to strain relief 420 and distal hub 418 to provide avalve structure for fluid tube 410. As shown in FIG. 27A, fluid tube 410extends through groove 414 from strain relief 420, through main body 422and distal hub 420 to tip 313. Rotation of sleeve 416 will impede, andeventually obstruct, the flow of fluid through tube 410. Of course, thisfluid control may be provided by a variety of other input and valvedevices, such as switches, buttons, etc.

In alternative embodiments, the fluid path may be directly formed inprobe 310 by, for example, a central inner lumen or an annular gap (notshown) within the handle and the tip. This inner lumen may be formednear the perimeter of the probe 310 such that the electricallyconductive fluid tends to flow radially inward towards the target site,or it may be formed towards the center of probe 310 so that the fluidflows radially outward. In addition, the electrically conductive fluidmay be delivered from a fluid delivery element (not shown) that isseparate from probe 310. In arthroscopic surgery, for example, the bodycavity will be flooded with isotonic saline and the probe 310 will beintroduced into this flooded cavity. Electrically conductive fluid willbe continually resupplied to maintain the conduction path between returnelectrode 400 and active electrodes 358. A more complete description ofalternative electrosurgical probes incorporating one or more fluidlumen(s) can be found in commonly assigned, co-pending application Ser.No. 08/485,219, filed on Jun. 7, 1995, the complete disclosure of whichis incorporated herein by reference.

Referring now to FIG. 26, electrically isolated active electrodes 358are spaced apart over tissue treatment surface 380 of electrode supportmember 370, preferably in a linear array. In the representativeembodiment, three active electrodes 358, each having a substantiallyconical shape, are arranged in a linear array extending distally fromsurface 380. Active electrodes 358 will usually extend a distance ofabout 0.5 mm to 20 mm from tissue treatment surface 380, preferablyabout 1 mm to 5 mm. Applicant has found that this configurationincreases the electric field intensities and associated currentdensities at the distal edges of active electrodes 358, which increasesthe rate of tissue cutting. In the representative embodiment, the tissuetreatment surface 380 has a circular cross-sectional shape with adiameter in the range of about 0.5 mm to 20 mm (preferably about 2 mm to10 mm). The individual active electrodes 358 preferably taper outward asshown, or they may form a distal edge, such as the electrodes shown inFIGS. 3 and 24.

Probe 430 of FIG. 28 includes a shaft 432 coupled to a proximal handle434 for holding and controlling shaft 432. Probe 430 includes an activeelectrode array 436 at the distal tip of shaft 432, an annular returnelectrode 438 extending through shaft 432 and proximally recessed fromthe active electrode array 436, and an annular lumen 442 between returnelectrode 438 and an outer insulating sheath 446. Probe 430 furtherincludes a liquid supply conduit 444 attached to handle 434 and in fluidcommunication with lumen 442, and a source of electrically conductivefluid (not shown) for delivering the fluid past return electrode 438 tothe target site on the tissue 440. Electrode array 436 is preferablyflush with the distal end of shaft 432 or distally extended from thedistal end by a small distance (on the order of 0.005 inches) so as tominimize the depth of ablation. Preferably, the distal end of shaft 432is beveled to improve access and control of probe 430 while treating thetarget tissue.

Yet another embodiment of the present invention is shown in FIG. 29.Auxiliary active electrodes 458, 459 are positioned at the distal tip 70of the probe. Auxiliary active electrodes 458, 459 may be the same sizeas ablation active electrodes 58, or larger as shown in FIG. 29. Oneoperating arrangement is to connect auxiliary active electrodes 458, 459to two poles of a high frequency power supply to form a bipolar circuitallowing current to flow between the terminals of auxiliary activeelectrodes 458, 459 as shown by current flux lines 460. Auxiliary activeelectrodes 458, 459 are electrically isolated from ablation electrodes58. By proper selection of the inter-electrode spacing, W₂, andelectrode width, W₃, and the frequency of the applied voltage, thecurrent flux lines 460 can be caused to flow below the target layer asdescribed above.

The voltage will preferably be sufficient to establish high electricfield intensities between the active electrode array 436 and the targettissue 440 to thereby induce molecular breakdown or disintegration ofseveral cell layers of the target tissue. As described above, asufficient voltage will be applied to develop a thin layer of vaporwithin the electrically conductive fluid and to ionize the vaporizedlayer or region between the active electrode(s) and the target tissue.Energy in the form of charged particles are discharged from the vaporlayer to ablate the target tissue, thereby minimizing necrosis ofsurrounding tissue and underlying cell layers.

With reference to FIG. 30, there is shown in perspective view anelectrosurgical probe 700, according to another embodiment of theinvention. Probe 700 includes a shaft 702 having a shaft distal endportion 702 a and a shaft proximal end portion 702 b. Shaft 702 isaffixed at its proximal end 702 b to a handle 704. Shaft 702 typicallycomprises an electrically conductive material, usually a metal, such astungsten, stainless steel, platinum or its alloys, titanium or itsalloys, molybdenum or its alloys, nickel or its alloys. An electricallyinsulating electrode support 710 is disposed at shaft distal end 702 a.An active electrode 712 is disposed on electrode support 710. Activeelectrode 712 comprises a blade electrode (e.g., FIGS. 31A, 31B). Anelectrically insulating sleeve 716 covers a portion of shaft 702, andterminates at sleeve distal end 716 a to define an exposed portion ofshaft 702 extending between electrode support proximal end 710 b andsleeve distal end 716 a. This exposed portion of shaft 702 defines areturn electrode 718 on shaft distal end portion 702 a. (In analternative embodiment, the return electrode may take the form of anannular band of an electrically conductive material, e.g., a platinumalloy, disposed on the exterior of the shaft distal end.) A cavitywithin handle 704 accommodates a connection block 706, which isconnected to active electrode 712 and return electrode 718 via electrodeleads (not shown). Connection block 706 provides a convenient mechanismfor coupling active electrode 712 and return electrode 718 to oppositepoles of a power supply (e.g., power supply 28, FIG. 1).

FIG. 31A is a perspective view of an active electrode 712 of probe 700,according to one embodiment of the invention. Active electrode 712 is inthe form of a single blade electrode which extends from electrodesupport 710 to a distance, H_(b). The distance H_(b) may vary, forexample, according to the intended applications of probe 700, and thevalue of H_(b) is at least to some extent a matter of design choice.Typically, for a broad array of electrosurgical procedures, the distanceH_(b) is in the range of from about 0.02 mm to about 5 mm. Activeelectrode 712 includes an active edge 713 which is adapted forgenerating high current densities thereat upon application of a highfrequency voltage from the power supply between active electrode 712 andreturn electrode 718. In this way, active edge 713 can efficientlyeffect localized ablation of tissues via molecular dissociation oftissue components which contact, or are in close proximity to, activeedge 713. A process for ablation of tissues via molecular dissociationof tissue components has been described hereinabove.

As best seen in FIG. 31B, the blade-like active electrode 712 furtherincludes first and second blade sides, 714 a, 714 b, respectively. Firstand second blade sides 714 a, 714 b are separated by a maximum distance,W_(b). The distance W_(b) is typically in the range of from about 0.1 mmto about 2.5 mm. In the embodiment of FIG. 31B, first and second bladesides 714 a, 714 b are substantially parallel to each other. Each offirst and second blade sides 714 a, 714 b are adapted for engagingtissue severed, ablated, or otherwise modified by active edge 713, andfor coagulating tissue engaged by first blade side 714 a and/or secondblade side 714 b. In this way, active electrode 712 can precisely andeffectively sever, ablate, or otherwise modify a target tissue withactive edge 713 to form a first-modified tissue, and at the same time,or shortly thereafter, further modify the first-modified tissue by meansof first and second blade sides 714 a, 714 b. For example, active edge713 can make an incision in a target tissue via localized moleculardissociation of target tissue components, while first and second bladesides 714 a, 714 b can effect hemostasis in the severed tissue.

FIGS. 32A, 32B, and 32C are a side view, a plan view, and an end view,respectively, of electrosurgical probe 700 having a blade-like activeelectrode 712, according to one embodiment of the invention. In theembodiment of FIGS. 32A-C, electrode support 710 is disposed at theterminus of shaft 702, and active electrode 712 is affixed to supportdistal end 710 a (e.g., FIG. 33A). However, other arrangements forelectrode support 710 and active electrode 712 are within the scope ofthe invention (e.g., FIGS. 34A-C, 35A-C). Active electrode 712 is in theform of a substantially flat metal blade. Active electrode 712 is shownas being substantially rectangular as seen from the side (FIG. 32A).However, various other shapes for active electrode 712 are within thescope of the invention (e.g., FIGS. 33C-E). FIG. 32C is an end view ofprobe 700 as seen along the lines 32C-32C of FIG. 32B, showing alaterally compressed region 703 of shaft 702. Laterally compressedregion 703 may be adapted for housing electrode support 710. Laterallycompressed region 703 may also facilitate manipulation of shaft distalend portion 702 a of probe 700 during various surgical procedures,particularly in situations where accessibility of a target tissue isrestricted.

FIGS. 33A and 33B are a side view and a plan view, respectively, of thedistal end of probe 700, showing details of shaft distal end portion 702a and terminally disposed blade active electrode 712, according to oneembodiment of the invention. Blade electrode 712 is substantiallyrectangular in shape as seen from the side (FIG. 33A). The distal end ofshaft 702 includes laterally compressed region 703. As seen from theside (FIG. 33A), laterally compressed region 703 appears wider than moreproximal portions of shaft 702. FIG. 33B is a plan view of probe 700 asseen along the lines 33B-33B of FIG. 33A, in which laterally compressedregion 703 appears narrower than more proximal portions of shaft 702.Electrode support 710 is mounted to the distal end of laterallycompressed region 703. Typically, electrode support 710 comprises adurable, electrically insulating, refractory material having a certainamount of flexibility. For example, electrode support 710 may comprise amaterial such as a silicone rubber, a polyimide, a fluoropolymer, aceramic, or a glass.

FIGS. 33C-33E each show a side view of the distal end of probe 700having a terminal blade active electrode 712, according to threedifferent embodiments of the invention. Electrode support 710 is mountedterminally on shaft 702, and includes a support distal end 710 a and asupport proximal end 710 b. In the embodiment of FIG. 33C, active edge713 of active electrode 712 is arcuate, convex, or substantiallysemi-circular in shape. In the embodiment of FIG. 33D, active electrode712 has a pointed active edge 713, while in the embodiment of FIG. 33E,the active edge 713 of active electrode 712 is serrated.

FIG. 34A shows in side view an electrosurgical probe 700 havingelectrode support 710 mounted terminally on shaft 702 and blade activeelectrode 712 disposed laterally on electrode support 710, according toanother embodiment of the invention. FIG. 34B is a plan view of probe700 taken along the lines 34B-34B of FIG. 34A. FIG. 34C is an end viewtaken along the lines 34C-34C of FIG. 34A. In the embodiments of FIGS.34A-C, electrode 712 is in the form a substantially flat, metal bladehaving first and second blade sides 714 a, 714 b, substantially parallelto each other. First and second blade sides 714 a, 714 b are adapted forengaging and coagulating severed or modified tissue, as describedhereinabove.

FIG. 35A shows in side view an electrosurgical probe 700 havingelectrode support 710 mounted laterally on the distal end of shaft 702,according to another embodiment of the invention. Blade active electrode712 is mounted laterally on electrode support 710. FIG. 35B is a planview of probe 700 taken along the lines 35B-35B of FIG. 35A. FIG. 35C isan end view taken along the lines 35C-35C of FIG. 35A. Active electrode712 is in the form a substantially flat, metal blade having first andsecond blade sides 714 a, 714 b, substantially parallel to each other.Electrode support 710 is mounted laterally on laterally compressedregion 703 of shaft 702.

FIG. 36A shows a side view of the distal end of an electrosurgical probe700, wherein shaft 702 includes a beveled end 728 to which electrodesupport 710 is mounted. Blade active electrode 712 is disposed onelectrode support 710. The arrangement of electrode support 710 andelectrode 712 on beveled end 728 may facilitate access of shaft distalend portion 702 a in general, and of electrode 712 in particular, to atarget tissue during various surgical procedures, particularly insituations where accessibility is restricted. FIG. 36B shows a side viewof the distal end of an electrosurgical probe 700, according to anotherembodiment of the invention. Shaft 702 includes a curved distal end 702a′. Electrode support 710 is mounted on distal end 702 a′, and bladeactive electrode 712 is affixed to electrode support 710. Curved distalend 702 a′ facilitates access of electrode 712 to a target tissue duringvarious surgical procedures.

Although in the embodiments of FIGS. 34A-C, 35A-C, and 36A-B activeelectrode 712 is shown as being substantially rectangular, thisrepresentation should not be construed as limiting these embodiments toa rectangular active electrode 712. Indeed, each of the embodiments ofFIGS. 34A-C, 35A-C, and 36A-B may have an active electrode 712 in abroad range of shapes, including those represented in FIGS. 33C-E.

FIG. 37A shows in side view an electrosurgical probe 700 having anexterior tube 724 arranged on shaft 702 and coupled at its proximal endto a connection tube 720 at handle 704. Exterior tube 724 may comprise aplastic tube of suitable length commensurate with the size of probe 700.Exterior tube 724 defines a lumen 726, and typically terminates at shaftdistal end 702 a at a location somewhat proximal to electrode support710. In some embodiments, probe 700 may include two or more exteriortubes 724, each exterior tube 724 having lumen 726. Each lumen 726 mayserve as a conduit for an aspiration stream, or as a conduit fordelivery of an electrically conductive fluid to the shaft distal end,generally as described hereinabove. FIG. 37B is an end view of probe 700taken along the lines 37B-37B of FIG. 37A, showing exterior tube 724 andlumen 726 in relation to shaft 702. The diameter of exterior tube 724is, at least to some extent, a matter of design choice. Exterior tube724 may comprise a substantially rigid or somewhat flexible plastic tubecomprising polyethylene, a polyimide, a fluoropolymer, and the like.

FIG. 38A shows, in side view, an electrosurgical probe 700 having anouter sheath 722 surrounding the exterior of a portion of shaft 702,according to another embodiment of the invention. Outer sheath 722 iscoupled at its proximal end to a connection tube 720 at handle 704.Outer sheath 722 may comprise a plastic tube of suitable length andhaving a diameter larger than that of shaft 702. Together with theexterior of shaft 702, outer sheath 722 defines a lumen 726′ in the formof an annular void. Typically, outer sheath 722 terminates at shaftdistal end 702 a at a location proximal to electrode support 710. Lumen726′ typically serves as a conduit for delivery of an electricallyconductive fluid to the shaft distal end. FIG. 38B is an end view ofprobe 700 taken along the lines 38B-38B of FIG. 38A, showing outersheath 722 and lumen 726′ in relation to shaft 702. The diameter ofouter sheath 722 is, at least to some extent, a matter of design choice.Outer sheath 722 may comprise a substantially rigid or somewhat flexibleplastic tube comprising polyethylene, a polyimide, and the like.

FIG. 39A schematically represents an electrosurgical probe 700,according to another embodiment of the invention. Probe 700 includesshaft 702 and handle 704 affixed at shaft proximal end 702 b. A firstelectrode support 711 a and a second electrode support 711 b aredisposed at shaft proximal end 702 a. A blade active electrode 712 isarranged on first and second electrode supports, 711 a, 711 b. Each offirst and second electrode supports 711 a, 711 b may comprise arefractory and electrically insulating material, such as a siliconerubber or the like, as described hereinabove. A return electrode 718 islocated at shaft distal end 702 proximal to first and second electrodesupports 711 a, 711 b. Return electrode 718 may comprise an exposedportion of shaft distal end 702 a (e.g., FIGS. 32A-C). Blade activeelectrode 712 typically extends distally from electrode support 710 by adistance in the range of from about 0.1 mm to about 10 mm, an moretypically from about 2 mm to 10 mm.

Blade active electrode 712 and return electrode 718 may be independentlycoupled to opposite poles of a high frequency power supply via electrodeleads (not shown) and a connection block (e.g., FIG. 30). In oneembodiment, an active electrode lead is coupled to one of first andsecond electrode arms 715 a, 715 b, and the other arm terminates in afree, electrically isolated end, for example, within first electrodesupport 711 a or second electrode support 711 b. Blade active electrode712 includes a crosspiece 715 c (FIGS. 39B-D) located distal toaspiration port 734. A fluid delivery element or unit including an outersheath 722′ (e.g., FIG. 39B) is omitted from FIG. 39A for the sake ofclarity.

FIG. 39B is a partial sectional view of probe 700 of FIG. 39A as seenfrom the side. Outer sheath 722′ defines an annular fluid delivery lumen726′ between sheath 722′ and shaft 702. Lumen 726′ terminates in anannular fluid delivery port 725 at shaft distal end 702 a. Fluiddelivery lumen 726′ is in communication proximally with a fluid deliverytube 721. Solid arrows indicate the direction of flow of an electricallyconductive fluid (e.g., isotonic saline) within fluid delivery lumen726′. An aspiration device of probe 700 includes aspiration port 734 incommunication with an aspiration lumen 732 and an aspiration tube 730.Solid arrows within aspiration lumen 732 indicate the direction of flowof an aspiration stream, which flows proximally from aspiration port 734towards a source of vacuum (not shown), the latter coupled to aspirationtube 730. Such an aspiration device enables convenient removal ofunwanted materials, for instance, excess extraneous fluid (e.g.,saline), resected tissue fragments, gaseous ablation by-products, andvapors, from the surgical field, thereby greatly improving visualizationof the surgical field.

During a procedure, the rate of suction or aspiration via the aspirationdevice will generally depend on a number of factors including thediameters of aspiration port 734, aspiration lumen 732, and aspirationtube 730. In one embodiment, the diameter of one or more of aspirationport 734, aspiration lumen 732, and aspiration tube 730 is selected soas to limit the rate of aspiration to a level that allows for continuousaspiration (when needed) during use of probe 700, without deflating thebody cavity or coelom. In one embodiment, the rate of aspiration or rateof flow of the aspiration stream may be controlled by an adjustablevalve (not shown). As an example, such a valve may be convenientlycoupled to aspiration tube 730, or connected between aspiration tube 730and the vacuum source.

FIG. 39C is an end view of probe 700 taken along the lines 39C-39C ofFIG. 39B. Active electrode 712 includes crosspiece 715 c extendingbetween first and second electrode arms 715 a, 715 b, respectively (FIG.39D). Active electrode 712 further includes first and second blade sides714 a, 714 b. In some embodiments, first and second blade sides 714 a,714 b are adapted for engaging tissue that has been severed, and forcoagulating the severed tissue. Crosspiece 715 c at least partiallyspans aspiration port 734. Typically, active electrode 712 comprises asingle metal blade, comprising a material such as platinum, tungsten,palladium, iridium, or titanium, or their alloys.

FIG. 39D shows detail of the distal portion of probe 700 of FIGS. 39A-Cincluding blade active electrode 712. As shown, first and secondelectrode arms 715 a, 715 b are disposed on first and second electrodesupports 711 a, 711 b, respectively. In an alternative embodiment, firstand second electrode arms 715 a, 715 b may be disposed on a singleannular electrode support having a substantially central void definingaspiration port 734. In one embodiment, active electrode 712 includesboth a distal active edge 713 a, and a proximal active edge 713 b.Distal active edge 713 a, in particular, is adapted for aggressivelyablating tissue via molecular dissociation of tissue components and forsevering tissue targeted for resection, transection, dissection, orother treatment.

FIG. 40A is a partial sectional view of an electrosurgical probe 700according to another embodiment of the invention. Probe 700 of FIG. 40Agenerally includes shaft 702 and handle 704, together with a fluiddelivery element, and an aspiration unit, essentially as for theembodiment described with reference to FIGS. 39A-D. In the interests ofbrevity these elements and features will not described in detail withreference to FIGS. 40A-C. The embodiment of FIG. 40A differs from otherembodiments described herein in having an active electrode in the formof a plasma hook 712′. Hook 712′ is in some respects analogous to plasmablade electrodes described hereinabove. For example, in one respect hook712′ is analogous to a truncated version of electrode 712 of theembodiment of FIGS. 39A-D in which one of arms 715 a or 715 b is omittedleaving one electrode arm affixed to crosspiece 715 c. From a functionalstandpoint, hook 712′ allows the operator (surgeon) to ablate tissue bydrawing the instrument towards himself/herself. In this manner, greatercontrol is exerted over the amount or extent of tissue removed orsevered by probe 700. Hook 712′ includes a first axial portion 712′a(FIG. 40C) in contact at its proximal end with electrode support 710.Hook 712′ may further include a second portion 712′b extending from thedistal portion of first axial portion 712′a. In some embodiments, secondportion 712′b is arranged substantially orthogonal to first axialportion 712′a. In one embodiment, second portion 712′b may bestructurally similar or analogous to crosspiece 715 c of the embodimentof FIGS. 39A-D. Second portion 712′b at least partially spans aspirationport 734 (FIG. 40B). Electrode support 710 may comprise a refractory andelectrically insulating material, such as a silicone rubber or the like,as described hereinabove.

FIG. 40B shows an end view of probe 700 taken along the lines 40B-40B ofFIG. 40A. Hook 712′ includes first and second blade sides 714 a, 714 b.Second portion 712′b extends at least partially across aspiration port734. FIG. 40C shows detail of the distal end portion of probe 700 ofFIGS. 40A, 40B, including hook 712′. Hook 712′ includes a distal activeedge 713 a, a proximal active edge 713 b, and an active tip 713 c.Return electrode 718 is located proximal to electrode support 710. Uponapplication of a high frequency voltage between hook 712′ and returnelectrode 718, a high current density may be generated at each of distalactive edge 713 a, proximal active edge 713 b, and active tip 713 c.Each of distal active edge 713 a, proximal active edge 713 b, and activetip 713 c may be adapted for severing tissue via electrosurgicalmolecular dissociation of tissue components.

FIGS. 41A, 41B, and 41C each show detail of the distal end portion of anelectrosurgical probe including a hook electrode 712′, according tothree different embodiments of the invention. In the embodiment of FIG.41A, hook 712′ is curved, having a convex distal edge 713 a, and aconcave proximal edge 713 b. In the embodiment of FIG. 41B, proximaledge 713 b includes serrations thereon. In an alternative embodiment(not shown), distal edge 713 a, and/or active tip 713 c may be similarlyserrated. In the embodiment of FIG. 41C, hook 712′ is curved, having aconcave distal edge 713 a, and a convex proximal edge 713 b. Accordingto various embodiments of probe 700, second portion 712′b may have alength which is less than, equal to, or greater than the diameter ofshaft 702. In the latter case, second portion 712′b extends laterallybeyond the exterior surface of shaft 702 (e.g., FIG. 41C). In each ofthe embodiments of FIGS. 41A-C, hook 712′ typically comprises a singleblade having first and second blade sides 714 a, 714 b (e.g., FIG. 40B).Hook 712′ typically comprises a metal such as platinum, tungsten,palladium, iridium, or titanium, or their alloys.

FIGS. 42A-B schematically represent a process during treatment of apatient with electrosurgical probe 700. Blade active electrode 712 isaffixed to support 710 on shaft 702. Blade active electrode 712 includesactive edge 713 and first and second blade sides, 714 a, 714 b (e.g.,FIGS. 31A-B). Referring to FIG. 42A, active edge 713 forms an incision,I, in a target tissue, T, via localized molecular dissociation of tissuecomponents upon application of a high frequency voltage between activeelectrode 712 and return electrode 718. (The localized moleculardissociation may be facilitated by the delivery of a suitable quantityof an electrically conductive fluid (e.g. isotonic saline) to form acurrent flow path between active electrode 712 and return electrode718.) With reference to FIG. 42B, as the incision I is deepened withintissue T, first and second blade sides, 714 a, 714 b engage severedtissue in regions indicated by the arrows labeled E. In this way, thesevered tissue is coagulated by first and second blade sides, 714 a, 714b, thereby effecting hemostasis at the point of incision of the tissue.

FIG. 43A schematically represents a number of steps involved in a methodof treating a patient with an electrosurgical probe, wherein step 1000involves positioning the distal end of the probe adjacent to targettissue such that an active electrode of the probe is in contact with orin close proximity to the target tissue. In one embodiment, the activeelectrode is spaced a short distance from the target tissue, asdescribed hereinabove. Typically, step 1000 involves positioning theprobe such that an active edge of the active electrode makes contactwith, or is in close proximity to, the target tissue. Step 1002 involvesdelivering an electrically conductive fluid to the distal end of theprobe in the vicinity of the active electrode and the return electrode,such that the electrically conductive fluid forms a current flow pathbetween the active electrode and the return electrode. The electricallyconductive fluid may be delivered via an exterior tube disposed on theoutside of the shaft (e.g., FIGS. 37A, 37B), or an outer sheath externalto the shaft and forming an annular fluid delivery lumen (e.g., FIGS.38A, 38B). The electrically conductive fluid may be a liquid, a gel, ora gas. Apart from providing an efficient current flow path between theactive and return electrodes, a clear, colorless electrically conductiveliquid, such as isotonic saline, exhibits the added advantage ofincreasing the visibility of the surgeon at the target site. However, insituations where there is an abundance of electrically conductive bodyfluids (e.g., blood, synovial fluid) already present at the target site,step 1002 may optionally be omitted.

Step 1004 involves applying a high frequency voltage between the activeelectrode and the return electrode sufficient to ablate or otherwisemodify the target tissue via localized molecular dissociation of targettissue components. By delivering an appropriate high frequency voltageto a suitably configured probe, the target tissue can be incised,dissected, transected, contracted, or otherwise modified. In addition,the modified tissue can also be coagulated (e.g., FIG. 42B). Thefrequency of the applied voltage will generally be within the rangescited hereinabove. For example, the frequency will typically range fromabout 5 kHz to 20 MHz, usually from about 30 kHz to 2.5 MHz, and oftenbetween about 100 kHz and 200 kHz. The root mean square (RMS) voltagethat is applied in step 1004 is generally in the range of from about 5volts RMS to 1000 volts RMS, more typically being in the range of fromabout 10 volts RMS to 500 volts RMS. The actual voltage applied maydepend on a number of factors, including the size of the activeelectrode, the operating frequency, and the particular procedure ordesired type of modification of the tissue (incision, contraction,etc.), as described hereinabove.

Step 1006 involves manipulating the probe with respect to the tissue atthe target site. For example, the probe may be manipulated such that anactive edge of a blade or hook electrode reciprocates with respect tothe target tissue, such that the target tissue is severed, incised, ortransected at the point of movement of the active edge by a processinvolving molecular dissociation of tissue components. In embodimentswhere the active electrode is in the form of a hook, step 1006 mayinvolve engaging the hook against the target tissue and drawing the hooktowards the operator in order to cut or sever the tissue. In thismanner, the extent of cutting or severing can be precisely controlled.In one embodiment, step 1006 involves reciprocating an active edge in adirection parallel to a surface of the target tissue. Typically, step1006 is performed concurrently with step 1004. Step 1002 may beperformed at any stage during the procedure, and the rate of delivery ofthe electrically conductive fluid may be regulated by a suitablemechanism, such as a valve.

Step 1008 involves modifying the target tissue as a result of the highfrequency voltage applied in step 1004. The target tissue may bemodified in a variety of different ways, as referred to hereinabove. Thetype of tissue modification achieved depends, inter alia, on the voltageparameters of step 1004; the shape, size, and composition of the activeelectrode; and the manner in which the probe is manipulated by thesurgeon in step 1006. At relatively high voltage levels, tissuecomponents typically undergo localized molecular dissociation, wherebythe target tissue can be dissected, incised, transected, etc. At a lowervoltage, or at a lower current density on the active electrode surface,the target tissue can be contracted (e.g., by shrinkage of collagenfibers in the tissue), or a blood vessel can be coagulated. For example,in step 1010 the first and second blade sides of the active electrodemay be engaged against a region of the target tissue which has beenmodified as a result of localized molecular dissociation of tissuecomponents in step 1008. The first and second blade sides aresubstantially flat metal plates having lower current densities than theactive edge. In this manner, the lower current densities of the firstand second blade sides effect further modification (e.g., coagulation)of the previously modified (e.g., severed) target tissue (step 1012).

FIG. 43B schematically represents a number of steps involved in a methodof severing tissue with an electrosurgical probe via a process involvingmolecular dissociation of tissue components, and of coagulating thesevered tissue with the same electrosurgical probe during a singleprocedure, according to one embodiment of the invention. Theelectrosurgical probe typically comprises an active electrode in theform of a single, substantially flat metal hook or blade having at leastone active edge adapted for electrosurgically severing the tissue, andfirst and second blade sides adapted for effecting hemostasis of thesevered tissue. Steps 1000′ through 1006′ are substantially the same oranalogous to steps 1000 through 1006, as described hereinabove withreference to FIG. 43A. Step 1008′ involves severing the target tissuevia localized molecular dissociation of tissue components due to highcurrent densities generated at the position of an active edge uponexecution of step 1004′. Step 1010′ involves engaging the first andsecond blade sides against the tissue severed in step 1008′, wherebyblood/blood vessels in the severed tissue are coagulated as a result ofthe relatively low current densities on the first and second blade sides(step 1012′).

FIG. 44 schematically represents a number of steps involved in a methodof dissecting a tissue or organ of a patient with an electrosurgicalprobe having a hook or blade active electrode, according to oneembodiment of the invention, wherein step 1100 involves accessing anorgan or tissue. Typically, accessing an organ or tissue in step 1100involves incising an overlying tissue which conceals the organ or tissueto be dissected. As an example, in an open chest procedure involving amedian stemotomy, the thoracic cavity is accessed by making alongitudinal incision though the sternum. Incising an overlying tissuein step 1100 may be performed generally according to the methodsdescribed with reference to FIG. 43A or 43B. Step 1102 involvespositioning the distal end of the electrosurgical probe, and inparticular an active edge of the hook or blade active electrode, in atleast close proximity to connective tissue adjacent to the tissue ororgan to be dissected. As an example, the connective tissue may be softtissue, such as adipose tissue, or relatively hard tissue such ascartilage or bone. Optional step 1104 involves delivering anelectrically conductive fluid to the distal end of the probe such thatthe electrically conductive fluid forms a current flow path between theactive electrode and the return electrode, generally as described forstep 1002, supra. Step 1106 involves applying a high frequency voltagebetween the active electrode and the return electrode, generally asdescribed for step 1004, supra.

Depending on the type of procedure, e.g., the nature of the tissue ororgan to be dissected, optional step 1108 may be performed, in which theprobe is manipulated such that an active edge of the active electrode ismoved with respect to the connective tissue adjacent to the tissue ororgan to be dissected. Where the active electrode comprises a hook, thehook may be engaged against the connective tissue and drawn towards theoperator of the probe to precisely control the degree of cutting ortissue removal. Step 1110 involves electrosurgically ablating, viamolecular dissociation of connective tissue components, at least aportion of the connective tissue adjacent to the tissue or organ to bedissected. As an example, connective tissue adjacent to the internalmammary artery may be dissected by a process involving moleculardissociation of connective tissue components, in either an open-chest ora minimally invasive procedure, such that the IMA is substantially freefrom connective tissue over a portion of its length.

FIG. 45A schematically represents an electrosurgical system 1200 of theinstant invention, including a high frequency power supply 1250, coupledto an active electrode 1212 and a return electrode 1218, for applying ahigh frequency voltage between active electrode 1212 and returnelectrode 1218. System 1200 is adapted for operating in a sub-ablationmode (e.g., a coagulation mode) or in an ablation mode. In particular,system 1200 is adapted for coagulating or otherwise modifying a targettissue while operating in the sub-ablation mode; and for ablating orsevering a target tissue while operating in the ablation mode. System1200 further includes an actuator unit 1230 coupled to at least one ofactive electrode 1212 and return electrode 1218. At least one of activeelectrode 1212 and return electrode 1218 is moveable upon actuation ofactuator unit 1230 by an operator of system 1200. Movement of at leastone of active electrode 1212 and return electrode 1218, via actuatorunit 1230, allows target tissue to be clamped by an electrosurgicalprobe during a surgical procedure and subsequently released, as will bediscussed fully hereinbelow.

FIG. 45B is a box diagram which schematically represents anelectrosurgical system 1200′, according to another embodiment of theinstant invention. System 1200′ includes power supply 1250, activeelectrode 1212, return electrode 1218, and actuator unit 1230, as forsystem 1200 of FIG. 45A. System 1200′ is similarly adapted forcoagulating, severing, ablating, or otherwise modifying a target tissue.System 1200′ further includes a mode switch 1240 coupled to bothactuator unit 1230 and power supply 1250. Mode switch 1240 is forswitching system 1200′ between an ablation mode and a sub-ablation modeupon actuation of actuator unit 1230. Actuation of actuator unit 1230enables movement of at least one of active electrode 1212 and returnelectrode 1218, and at the same time signals mode switch 1240 to switchsystem 1200′ between the ablation and sub-ablation modes. In particular,actuator unit 1230 is adapted for shifting a probe (e.g., FIG. 47)between a closed configuration and an open configuration, such that thesystem operates in the sub-ablation mode when the probe is in the closedconfiguration, and the system operates in the ablation mode when theprobe is in the open configuration.

In one embodiment, actuator unit 1230 provides a variable response,whereby the extent or degree of movement of active electrode 1212 and/orreturn electrode 1218 can be controlled. The ablation mode ischaracterized by a relatively high voltage applied by power supply 1250between active electrode 1212 and return electrode 1218, whereas thesub-ablation mode is characterized by a relatively low voltage, asdescribed in detail hereinabove. Typically, the ablation mode ischaracterized by a high frequency voltage in the range of from about 200volts RMS to 1800 volts RMS, more typically from about 500 volts RMS to1500 volts RMS. The sub-ablation mode is typically characterized by ahigh frequency voltage in the range of from about 10 volts RMS to 1000volts RMS, more typically from about 50 volts RMS to 250 volts RMS. Theablation mode is adapted for ablating or severing target tissue viavaporization or, preferably, localized molecular dissociation of tissuecomponents, while the sub-ablation mode is adapted for coagulating orcontracting target tissue.

FIG. 45C is a box diagram which schematically represents anelectrosurgical system 1200″, according to another embodiment of theinvention. System 1200″ includes power supply 1250, active electrode1212, return electrode 1218, and actuator unit 1230, as for system 1200of FIG. 45A. System 1200″ is also adapted for coagulating, severing,ablating, or otherwise modifying a target tissue while operating in theablation mode or the sub-ablation mode, as for systems 1200, 1200′. Inthe embodiment of FIG. 45C, actuator unit 1230 is coupled to at leastone of active electrode 1212 and return electrode 1218, wherein at leastone of active electrode 1212 and return electrode 1218 is moveablebetween a first configuration and a second configuration. Actuation ofactuator unit 1230 effects movement of active electrode 1212 and/orreturn electrode 1218 such that a probe 1201 (e.g., FIG. 47) of system1200″ is shifted between the first configuration and the secondconfiguration.

System 1200″ further includes mode switch 1240 coupled to power supply1250 and to at least one of active electrode 1212 and return electrode1218. Mode switch 1240 is for switching system 1200″ between theablation mode and the sub-ablation mode upon shifting of probe 1201between the first configuration and the second configuration viaactuation of actuator unit 1230. Thus in the embodiment of system 1200″,actuation of actuator unit 1230 effects shifting of probe 1201 betweenthe first and second configurations, essentially as for system 1200′. Incontrast to system 1200′, in the embodiment of system 1200″, mode switch1240 is responsive to movement of active electrode 1212 or movement ofreturn electrode 1218, such that system 1200″ is switched between theablation and sub-ablation modes as the probe shifts between the firstand second configuration. In both system 1200′ and system 1200″, modeswitch 1240 may be integrated with actuator unit 1230, integrated withpower supply 1250, or may be a separate device.

FIG. 46 is a block diagram representing actuator unit 1230 of anelectrosurgical system of the invention, e.g., system 1200′ or 1200″(FIGS. 45B, 45C). As shown, actuator unit 1230 includes a clamp unit1232 and a release unit 1234. Clamp unit 1232 and release unit 1234 maybe in communication with each other. Clamp unit 1232 is for urging anelectrosurgical probe (e.g., probe 1201, FIG. 48C) towards a closedconfiguration such that a target tissue or portion of a blood vessel canbe clamped by the probe during a surgical procedure.

Clamp unit 1232 may take various forms and may function in a number ofdifferent ways. For example, clamp unit 1232 may be manually operated bythe exertion of a mechanical force on clamp unit 1232 by the surgeon,may take the form of a switch for turning on power to an electricallypowered mechanism (not shown) for effecting clamping of tissue, or maytake the form of a closure spring (also not shown) arranged so as toforce the probe towards the closed configuration. Release unit 1234 maysimilarly take various forms, for example, release unit 1234 may beoperated by the exertion, by the surgeon, of a counteracting mechanicalforce, via release unit 1234, sufficient to exceed the force exerted bya closure spring of clamp unit 1232. One or both of clamp unit 1232 andrelease unit 1234 may be hand- or foot-operated. For example, actuatorunit 1230 may comprise one or more foot pedals, or actuator unit 1230may be affixed to a handle of the probe (e.g., FIG. 47) for handoperation.

FIG. 47 is a side view of an electrosurgical probe 1201 including ashaft 1202 having a shaft distal end portion 1202 a and a shaft proximalend portion 1202 b. An active electrode 1212 and a return electrode 1218are disposed at shaft distal end portion 1202 a. Active electrode 1212is arranged on an electrically insulating electrode support 1210 forelectrically isolating active electrode 1212 from other components ofprobe 1201. At least one of active electrode 1212 and return electrode1218 is moveable such that shaft distal end portion 1202 a can adopt aclosed configuration or an open configuration. In one embodiment, activeelectrode 1212 and return electrode 1218 are in opposition to eachother. Shaft distal end portion 1202 a as shown in FIG. 47 is in theclosed configuration, wherein active electrode 1212 and return electrode1218 are parallel or substantially parallel to each other. In the openconfiguration, e.g., FIG. 48B, active and return electrodes 1212, 1218are parted. In one embodiment, active electrode 1212 is fixed and returnelectrode 1218 takes the form of a moveable, or removeable, cowl (e.g.,FIGS. 48B-E, 50A, 51).

A handle 1204 is affixed to shaft proximal end 1202 b. Handle 1204accommodates a connection block 1206, the latter in communication withactive electrode 1212 and return electrode 1218 via electrode leads (notshown in FIG. 47). As shown, actuator unit 1230 is affixed to, orintegral with, handle 1204. Actuator unit 1230 effects movement of oneor both of active electrode 1212 and return electrode 1218, therebyenabling probe 1201 to be shifted between the closed configuration andthe open configuration. Mode switch 1240 (FIGS. 45B, 45C) may beintegral with actuator unit 1230 and/or handle 1204. Connection block1206 provides for convenient coupling of active electrode 1212 andreturn electrode 1218 to power supply 1250. Mode switch 1240 may also beconnected to power supply 1250 via connection block 1206. Actuator unit1230 may also be coupled to active electrode 1212 and return electrode1218 via connection block 1206. The components of probe 1201, includingactive electrode 1212 and electrode support 1210, may be constructedfrom the same or similar materials as described for the correspondingcomponents of other probes of the invention, for example, probe 700described with reference to FIGS. 30-41C, supra.

FIGS. 48A-E each show detail of shaft distal end portion 1202 a of anelectrosurgical probe 1201 having a moveable return electrode 1218,according to one embodiment of the invention. FIG. 48A is a perspectiveview of shaft distal end portion 1202 a in which return electrode 1218is omitted for the sake of clarity. Electrode support 1210 is arrangedon a recessed portion 1203 of shaft 1202. In the embodiment as shown,active electrode 1212 protrudes both laterally and terminally fromelectrode support 1210. Active electrode 1212 is adapted for coagulatingand severing target tissue, as described in detail hereinbelow, during abroad range of surgical procedures. In one embodiment, active electrode1212 may be in the form of a blade electrode, for example, havingfeatures and characteristics similar to those described hereinabove foractive electrode 712 of probe 700 (e.g., FIGS. 30-41C).

FIG. 48B is a perspective view of shaft distal end 1202 a in an open orpartially open configuration, in which return electrode 1218 is pivotedabout its proximal end away from active electrode 1212. In the openconfiguration shaft distal end 1202 a can accommodate at least a portionof a target tissue or blood vessel, BV, between active electrode 1212and return electrode 1218. As shown, active electrode 1212 includes anelongate lateral portion 1212 a and a distal terminal portion 1212 b.Return electrode 1218 includes a return electrode perimeter 1222. In oneembodiment, return electrode 1218 includes a distal notch 1220 foraccommodating active electrode 1212. Notch 1220 prevents shortingbetween active electrode 1212 and return electrode 1218 when shaftdistal end 1202 a adopts the closed configuration (FIG. 48C). Returnelectrode 1218 may be forced into the open configuration and urgedtowards the closed configuration by actuator unit 1230 (e.g., FIG. 47).

FIG. 48C is a perspective view of shaft distal end 1202 a in the closedconfiguration, in which return electrode 1218 lies parallel to activeelectrode 1212. Return electrode 1218 is in the form of a cowl, whichlargely conceals electrode lateral portion 1212 a. Notch 1220accommodates electrode lateral portion 1212 a and allows returnelectrode 1218 to adopt a fully closed configuration. As shown,electrode terminal portion 1212 b protrudes distally from the distalterminus of probe 1201. In the closed configuration, probe 1201 may beused in the sub-ablation mode for coagulating or contracting tissue.Alternatively, probe 1201 may also be used in the closed configurationin the ablation mode, for ablating or severing tissue with electrodeterminal portion 1212 b. In the open configuration, probe 1201 may beused in the ablation mode for ablating or severing tissue with one orboth of lateral portion 1212 a and terminal portion 1212 b.

FIG. 48D is a sectional view of shaft distal end 1202 a in the closedconfiguration, as taken along the lines 48D-48D of FIG. 48C. It can beseen that when shaft distal end 1202 a is in the closed configuration, agap H_(g) exists between active electrode 1212 and the cowl of returnelectrode 1218. Typically, the gap H_(g) is in the range of from about0.05 mm to 10 mm, and more typically from about 1.0 mm to 10 mm. FIG.48E is a side view of shaft distal end 1202 a in the open or partiallyopen configuration, in which return electrode 1218 is arranged at anangle ∀ to active electrode 1212. Typically, when shaft distal end 1202a is in the open or partially open configuration, angle ∀ is in therange of from about 30° to 180°, and more typically in the range of fromabout 45° to 180°. In one embodiment, the extent to which returnelectrode 1218 pivots away from active electrode 1212 can be controlledvia actuator unit 1230. Typically, lateral portion 1212 a protrudeslaterally from electrode support 1210 by a distance D_(l). Typically thedistance D_(l) is in the range of from about 0.05 mm to 10 mm, and moretypically from about 0.5 mm to 8 mm. Electrode terminal portion 1212 btypically protrudes distally from electrode support 1210 by a distanceD_(d), in the range of from about 0.2 mm to 10 mm, and more typicallyfrom about 0.5 mm to 10 mm.

FIG. 49A shows shaft distal end portion 1202 a of an electrosurgicalprobe 1201 in the open or partially open configuration, according toanother embodiment of the invention. Perimeter 1222 of return electrode1218 includes an undulating portion 1222′. A shaft undulating portion1202 a′ of shaft distal end 1202 a undulates in a manner complementaryto perimeter undulating portion 1222′. As seen in FIG. 49B, when shaftdistal end portion 1202 a is in the closed configuration, the twoundulating surfaces of portions 1222′, 1202′ are “interlocked.” Thepresence of interlocking undulating surfaces of perimeter portion 1222′and shaft portion 1202′ facilitates grasping and clamping of targettissue during use of probe 1201.

FIG. 50A is a perspective view of a shaft distal end portion 1202 a ofan electrosurgical probe 1201 including an active electrode 1212′mounted terminally on electrode support 1210, and a moveable returnelectrode 1218. The embodiment of FIGS. 50A-C differs from thatdescribed with reference to FIGS. 47-49B in that active electrode 1212′does not extend or protrude laterally on shaft distal end portion 1202a. FIGS. 50B and 50C are side views of shaft distal end portion 1202 ain the open and closed configurations, respectively. In the embodimentof FIGS. 50A-C, return electrode 1218 is in the form of a quasidome-shaped cowl mounted on recessed portion 1203 of shaft 1202. Thepivotable nature of return electrode 1218 is indicated by thedouble-headed curved arrow marked A in FIG. 50B. As can be seen in FIG.50C, when shaft distal end portion 1202 a is in the closedconfiguration, a gap exists between active electrode 1212′ and returnelectrode 1218. The presence of the gap prevents shorting between activeelectrode 1212′ and return electrode 1218. Return electrode 1218 isadapted for clamping a target tissue or blood vessel against activeelectrode 1212′. In the closed configuration, with the probe operatingin the sub-ablation mode, active electrode 1212′ is adapted forcoagulating or contracting target tissue clamped between activeelectrode 1212′ and return electrode 1218. In the open configuration,with the probe operating in the ablation mode, active electrode 1212′ isadapted for ablating or severing target tissue via localized moleculardissociation of tissue components.

With reference to FIG. 51 there is shown a shaft distal end portion 1202a of an electrosurgical probe 1201 according to another embodiment ofthe invention. A moveable return electrode 1218′ comprises a cowl whichis pivotable laterally, as indicated by the double-headed curved arrowmarked A′ in FIG. 51. Return electrode 1218′ includes notch 1220 foraccommodating active electrode 1212 when shaft distal end portion 1202 ais in the closed configuration, thus preventing shorting between activeand return electrodes 1212, 1218′, respectively. Active electrode 1212may comprise an elongate metal blade, which protrudes distally andlaterally from electrode support 1210. While in the open configuration,shaft distal end portion 1202 a may be positioned such that a targettissue lies between active electrode 1212 and return electrode 1218′.Return electrode 1218′ may then be urged towards the closedconfiguration, e.g., by actuator unit 1230, whereby the target tissue isclamped between active electrode 1212 and return electrode 1218′. Inuse, active electrode 1212 and return electrode 1218′ are coupled toopposite poles of a high frequency power supply for applying a highfrequency voltage between active electrode 1212 and return electrode1218′.

FIGS. 52A and 52B show a shaft distal end portion 1202 a of anelectrosurgical probe 1201 in the closed configuration, and in the openor partially open configurations, respectively, according to anotherembodiment of the invention. In the closed configuration shown in FIG.52A, a fixed return electrode 1218″ lies substantially parallel to amoveable active electrode 1212″. Active electrode 1212″ may be moved,e.g., via actuation of actuation unit 1230, such that shaft distal endportion 1202 a is shifted to an open or partially open configuration,e.g., FIG. 52B. In one embodiment, active electrode 1212″ may pivotabout its proximal end, as indicated by the double-headed curved arrowmarked A″. When urged towards the closed configuration, active electrode1212″ combines with opposing return electrode 1218″ to effectively clamptarget tissue or a blood vessel at shaft distal end portion 1202 a.Tissue clamped between active electrode 1212″ and return electrode 1218″may be first coagulated by application of a first high frequency voltagefrom power supply 1250 operating in the sub-ablation/coagulation mode,and subsequently the coagulated tissue may be ablated by application ofa second high frequency voltage from power supply 1250 operating in theablation mode. Switching between the sub-ablation and ablation modes maybe controlled by mode switch 1240. As described hereinabove, mode switch1240 may be responsive either to actuation of actuator unit 1230 (e.g.,system 1200′, FIG. 45B), or to movement of active electrode 1212″ (e.g.,resulting in a change in configuration of shaft distal end 1202 a).

FIG. 53A schematically represents a number of steps involved in a methodof coagulating and severing a target tissue with an electrosurgicalprobe, wherein step 1300 involves advancing the electrosurgical probetowards the target tissue. The probe typically includes opposing activeand return electrodes arranged at a shaft distal end portion, wherein atleast one of the active and return electrodes is moveable such that theshaft distal end portion can adopt an open configuration or a closedconfiguration. Step 1302 involves configuring the probe such that theshaft distal end is in the open or partially open configuration.Typically, in the open configuration, the probe can accommodate at leasta portion of a target tissue and/or a portion of a blood vessel betweenthe active and return electrodes. The probe may be configured to theopen configuration via an actuator unit, for example, by actuation of arelease unit of the actuator unit.

Step 1304 involves positioning the target tissue between the active andreturn electrodes. Step 1306 involves configuring the probe such thatthe shaft distal end is in the closed or partially closed configuration.For example, the active electrode and/or the return electrode may beurged towards the closed configuration via actuation of a clamp unit ofthe actuator unit. In this manner, the target tissue, e.g., a portion ofa blood vessel, may be clamped between the active electrode and thereturn electrode. The clamp unit and the release unit may be hand- orfoot-operated by the surgeon, as described hereinabove, e.g., withreference to FIG. 46.

Step 1308 involves applying a first high frequency voltage between theactive electrode and the return electrode. Typically, the first highfrequency voltage is sufficient to coagulate the target tissue, butinsufficient to ablate the tissue via molecular dissociation of tissuecomponents, i.e., the system is operating in the sub-ablation mode. Step1310 involves coagulating the target tissue or blood vessel as a resultof the voltage applied in step 1308. Thereafter, step 1312 involvesapplying a second high frequency voltage between the active electrodeand the return electrode sufficient to ablate, or Coblate, the tissuevia molecular dissociation of tissue components. That is to say, duringstep 1308 the system is operating in the ablation mode. Voltage levelscharacteristic of the sub-ablation mode and the ablation mode arepresented hereinabove.

According to one aspect of the invention, during a procedure theelectrosurgical system may be conveniently switched, “automatically,”between the sub-ablation and ablation modes via a mode switch (FIGS.45B-C). In one embodiment of the invention (FIG. 45B), the mode switchmay be directly responsive to actuation of the actuator unit, such thatthe system is automatically switched to the ablation mode when therelease unit is actuated to force the probe into the open configuration.Similarly, the system may be automatically switched to the sub-ablationmode when the clamp unit is actuated to urge the probe into the closedconfiguration. According to an alternative embodiment (FIG. 45C), themode switch may be responsive to movement of a moveable electrode(either a moveable active electrode (FIGS. 52A-B) or a moveable returnelectrode (FIGS. 48B-D), such that the system is automatically switchedto the ablation mode when the at least one moveable electrode is movedinto the open configuration, and/or the system is automatically switchedto the sub-ablation mode when the at least one moveable electrode ismoved into the closed configuration. Optional step 1314 involvesmanipulating the probe during step 1312, such that the active electrodeis engaged and moved against the coagulated target tissue. As a resultof application of the second high frequency voltage the coagulatedtarget tissue is severed due to the localized molecular dissociation oftissue components, step 1316.

FIG. 53B schematically represents a number of steps involved in a methodof modifying and/or ablating a target tissue with an electrosurgicalsystem including a probe and a high frequency power supply, wherein step1400 involves clamping a target tissue. In one aspect, the target tissuemay comprise a portion of a blood vessel. For example, during resectionof a connective tissue via electrosurgical ablation, the surgeon mayencounter one or more substantial blood vessels which requirecoagulation before proceeding with the resection. Upon encountering sucha blood vessel, the surgeon may coagulate the blood vessel, as follows.With the electric power from the power supply turned off, or with theelectrosurgical system operating in a sub-ablation mode, the bloodvessel may be clamped between the active and return electrodes,essentially as described hereinabove, e.g., with reference to FIG. 53A.Thereafter, with the electrosurgical system in the sub-ablation mode,step 1402 involves applying a first high frequency voltage between theactive electrode and the return electrode, wherein the first highfrequency voltage is effective in coagulating the blood vessel, butinsufficient to ablate the blood vessel. As used in this context, theterm “ablate” refers to electrosurgical ablation via moleculardissociation of tissue components at relatively low temperatures(typically in the range of about 45° C. to 90° C.).

While the blood vessel or other target tissue remains clamped by theprobe, step 1404 involves coagulating the clamped blood vessel or othertarget tissue as a result of the first high frequency voltage applied instep 1402. After coagulation has occurred to a suitable extent, optionalstep 1406 involves releasing or unclamping the clamped vessel or othertarget tissue from the probe. Typically, releasing the target tissueinvolves configuring the probe to the open or partially openconfiguration, e.g., via a release unit of the electrosurgical system(FIG. 46). Thereafter, the electrosurgical system is switched to theablation mode, and a second, higher voltage is applied between theactive electrode and the return electrode in step 1408, wherein thesecond voltage is sufficient to ablate the coagulated tissue viamolecular dissociation of tissue components.

With the probe in the open configuration, the probe may be manipulatedby the surgeon such that the active electrode is engaged and movedagainst the coagulated tissue, step 1410. Step 1412 involves severingthe coagulated tissue via localized molecular dissociation of tissuecomponents. In the example cited above, namely wherein a blood vessel isencountered during resection of a tissue, after the blood vessel hasbeen coagulated and severed according to steps 1400 through 1412, withthe system operating in the ablation mode, the surgeon may then resumeresection via molecular dissociation of tissue components. Duringresection of tissue such as connective tissue, the probe will typicallybe in the open configuration (e.g., FIG. 48E). However, in embodimentsof probe 1201 in which the active electrode protrudes both laterally anddistally from the electrode support (e.g., FIGS. 48A-C), the probe mayalso be used in the closed configuration for ablation or modification oftarget tissue.

It is to be understood that the electrosurgical apparatus of theinvention is by no means limited to those methods described withreference to FIGS. 42A-44, or FIGS. 53A-B. Thus, as stated hereinabove,embodiments of an electrosurgical probe are applicable to a broad rangeof surgical procedures, such as ablation, incision, contraction,coagulation, or other modification of: connective tissue, includingadipose tissue, cartilage, and bone; dermal tissue; vascular tissues andorgans, including arteries and veins; and tissues of the shoulder, knee,and other joints. Thus, while the exemplary embodiments of the presentinvention have been described in detail, by way of example and forclarity of understanding, a variety of changes, adaptations, andmodifications will be apparent to those of skill in the art. Therefore,the scope of the present invention is limited solely by the appendedclaims.

1. An electrosurgical system for ablating or modifying tissue at atarget site, comprising: a shaft having a shaft distal end portion and ashaft proximal end portion, the shaft distal end portion having anactive electrode and an opposing return electrode in pivotablerelationship with said active electrode such that said electrodes havean open configuration or a closed configuration and wherein the closedconfiguration is adapted to clamp and hold tissue between the first andsecond electrode; a voltage supply in electrical communication with saidactive and return electrode; an electrically conductive fluid supplyassembly containing electrically conductive fluid having an electricalconductivity equal to or greater than isotonic saline, wherein theelectrically conductive fluid supply assembly is adapted to supplyelectrically conductive fluid to the target site such that a currentflow path is present through the electrically conductive fluid betweenthe active and the return electrode when a first high frequency voltageis applied between the active electrode and the return electrode; a modeswitch for switching the system between a coagulation mode and anablation mode, wherein the mode switch is responsive to a shift inconfiguration of the shaft distal end portion.
 2. The system of claim 1,wherein the closed configuration is adapted for coagulating a targettissue.
 3. The system of claim 1, wherein the first high frequencyvoltage is sufficient to ablate the target tissue via localizedmolecular dissociation of target tissue components.
 4. The system ofclaim 1 further comprising an electrode support supporting the activeelectrode.
 5. The system of claim 4, wherein the closed configuration isadapted for coagulating a target tissue.
 6. The system of claim 1wherein the return electrode comprises a notch adapted to accommodatethe active electrode.
 7. The system of claim 1 wherein the activeelectrode comprises an elongate lateral portion.
 8. The system of claim7 wherein the active electrode comprises a distal terminal portion. 9.The system of claim 1 comprising an actuator unit adapted to force theactive electrode and the return electrode toward the closedconfiguration.
 10. The system of claim 1 wherein the active electrode isparallel to the return electrode in the closed configuration.
 11. Thesystem of claim 1 wherein the return electrode comprises a cowl.
 12. Thesystem of claim 1 wherein in the open configuration the active electrodeis disposed at an angle with respect to the return electrode.
 13. Anelectrosurgical system for ablating or modifying tissue at a targetsite, comprising: a shaft having a shaft distal end portion and a shaftproximal end portion, the shaft distal end portion having an activeelectrode and an opposing return electrode in pivotable relationshipwith said active electrode such that said electrodes have an openconfiguration or a closed configuration and wherein the closedconfiguration is adapted to clamp and hold tissue between the first andsecond electrode; a voltage supply in electrical communication with saidactive and return electrode; and a mode switch for switching the systembetween a coagulation mode and an ablation mode, wherein the mode switchis responsive to a shift in configuration of the shaft distal endportion.
 14. The system of claim 13, further comprising an electrodesupport supporting the active electrode.
 15. The system of claim 13wherein the return electrode comprises a notch adapted to accommodatethe active electrode.
 16. The system of claim 13 wherein the activeelectrode comprises an elongate lateral portion.
 17. The system of claim16 wherein the active electrode comprises a distal terminal portion. 18.The system of claim 13 comprising an actuator unit adapted to force theactive electrode and the return electrode toward the closedconfiguration.
 19. The system of claim 13 wherein the active electrodeis substantially parallel to the return electrode in the closedconfiguration.
 20. The system of claim 13 wherein the return electrodecomprises a cowl.
 21. The system of claim 13 wherein in the openconfiguration the active electrode is disposed at an angle with respectto the return electrode.